''' ----------------------------------------------------------------------------------------------------
''' <summary>
''' Prints a text document.
''' </summary>
''' ----------------------------------------------------------------------------------------------------
''' <seealso cref="IDisposable" />
''' ----------------------------------------------------------------------------------------------------
Public Class PrintDocumentBasic : Implements IDisposable
 
#Region " Private Fields "
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' A <see cref="StreamReader"/> instance that encapsulates the document data to be read and printed.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    Protected documentStream As StreamReader
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' The <see cref="System.Drawing.Printing.PrintDocument"/> component to print the document.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    Protected WithEvents PrintDocument As PrintDocument
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' The <see cref="System.Drawing.Printing.PrinterSettings"/> instance that specifies 
    ''' information about how a document is printed, including the printer that prints it.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    Protected PrinterSettings As PrinterSettings
 
#End Region
 
#Region " Properties "
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Gets the document file path.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <value>
    ''' The document file path.
    ''' </value>
    ''' ----------------------------------------------------------------------------------------------------
    Public ReadOnly Property Filepath As String
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Gets or sets the text encoding.
    ''' <para></para>
    ''' If no encoding is specified, the default system encoding will be used.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <value>
    ''' The text encoding.
    ''' </value>
    ''' ----------------------------------------------------------------------------------------------------
    Public Property Encoding As Encoding
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Gets or sets the name of the printer device. 
    ''' <para></para>
    ''' If no printer name is specified, the default printer device will be used.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <value>
    ''' The name of the printer device.
    ''' </value>
    ''' ----------------------------------------------------------------------------------------------------
    Public Property PrinterName As String
        Get
            Return Me.printerNameB
        End Get
        Set(ByVal value As String)
            If Not String.IsNullOrEmpty(value) Then
                Me.PrinterSettings.PrinterName = Me.PrinterName
            Else
                ' Reset the 'PrinterSettings.PrinterName' property to avoid 'PrinterSettings.IsValid' return False.
                Me.PrinterSettings = New PrinterSettings()
            End If
        End Set
    End Property
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' ( Backing Field )
    ''' <para></para>
    ''' The name of the printer device.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    Private printerNameB As String
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Gets or sets the text font.
    ''' <para></para>
    ''' Default font is: [Font: Name=Arial, Size=10, Units=3, GdiCharSet=1, GdiVerticalFont=False]
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <value>
    ''' The text font.
    ''' </value>
    ''' ----------------------------------------------------------------------------------------------------
    Public Property Font As Font
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Gets or sets the text color.
    ''' <para></para>
    ''' Default color is: <see cref="System.Drawing.Color.Black"/>
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <value>
    ''' The text color.
    ''' </value>
    ''' ----------------------------------------------------------------------------------------------------
    Public Property Color As Color
 
#End Region
 
#Region " Constructors "
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Prevents a default instance of the <see cref="PrintDocumentBasic"/> class from being created.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    <DebuggerNonUserCode>
    Private Sub New()
    End Sub
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Initializes a new instance of the <see cref="PrintDocumentBasic"/> class.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <param name="filepath">
    ''' The document file path.
    ''' </param>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <exception cref="FileNotFoundException">
    ''' </exception>
    ''' ----------------------------------------------------------------------------------------------------
    <DebuggerStepThrough>
    Public Sub New(ByVal filepath As String)
        Me.New(filepath, encoding:=Nothing)
    End Sub
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Initializes a new instance of the <see cref="PrintDocumentBasic"/> class.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <param name="filepath">
    ''' The document file path.
    ''' </param>
    ''' 
    ''' <param name="encoding">
    ''' The text encoding.
    ''' </param>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <exception cref="FileNotFoundException">
    ''' </exception>
    ''' ----------------------------------------------------------------------------------------------------
    <DebuggerStepThrough>
    Public Sub New(ByVal filepath As String, ByVal encoding As Encoding)
        Me.PrintDocument = New PrintDocument() With {
            .DocumentName = filepath
        }
 
        Me.Filepath = filepath
        Me.Color = Color.Black
 
        Me.PrinterName = ""
 
        If (encoding Is Nothing) Then
            Me.documentStream = New StreamReader(filepath, detectEncodingFromByteOrderMarks:=True)
            Me.Encoding = Me.documentStream.CurrentEncoding
        Else
            Me.Encoding = encoding
            Me.documentStream = New StreamReader(filepath, encoding, detectEncodingFromByteOrderMarks:=False)
        End If
    End Sub
 
#End Region
 
#Region " Public Methods "
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Prints the current document.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <exception cref="IOException">
    ''' No printer device is installed.
    ''' </exception>
    ''' 
    ''' <exception cref="ArgumentException">
    ''' Printer name is not valid.
    ''' </exception>
    ''' ----------------------------------------------------------------------------------------------------
    <DebuggerStepThrough>
    Public Overridable Sub Print()
 
        If (PrinterSettings.InstalledPrinters.Count = 0) Then
            Throw New IOException("No printer device is installed.")
        End If
 
        If Not String.IsNullOrEmpty(Me.PrinterSettings.PrinterName) AndAlso Not (Me.PrinterSettings.IsValid) Then
            Throw New Exception("Printer name is not valid.")
        End If
 
        Me.PrintDocument.PrinterSettings = Me.PrinterSettings
        Me.PrintDocument.Print()
 
    End Sub
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Cancels the print job for the current document.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <exception cref="Exception">
    ''' Print job not found.
    ''' </exception>
    ''' ----------------------------------------------------------------------------------------------------
    <DebuggerStepThrough>
    Public Overridable Sub CancelPrint()
 
        Dim scope As New ManagementScope("root\CIMV2")
        Dim query As New SelectQuery(String.Format("SELECT * FROM Win32_PrintJob WHERE Document = '{0}'", Me.PrintDocument.DocumentName))
        Dim options As New EnumerationOptions With {
                .ReturnImmediately = True,
                .Rewindable = False,
                .DirectRead = True,
                .EnumerateDeep = False
            }
 
        Using mos As New ManagementObjectSearcher(scope, query, options),
              moc As ManagementObjectCollection = mos.Get()
 
            If (moc.Count = 0) Then
                Throw New Exception("Print job not found.")
            End If
 
            For Each mo As ManagementObject In moc
                mo.Delete()
            Next mo
 
        End Using
 
    End Sub
 
#End Region
 
#Region " Event-Handlers "
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Handles the <see cref="System.Drawing.Printing.PrintDocument.BeginPrint"/> event 
    ''' of the <see cref="PrintDocumentBasic.PrintDocument"/> component.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <param name="sender">
    ''' The source of the event.
    ''' </param>
    ''' 
    ''' <param name="e">
    ''' The <see cref="PrintEventArgs"/> instance containing the event data.
    ''' </param>
    ''' ----------------------------------------------------------------------------------------------------
    <DebuggerStepperBoundary>
    Protected Overridable Sub PrintDocument_BeginPrint(ByVal sender As Object, ByVal e As PrintEventArgs) Handles PrintDocument.BeginPrint
        If (Me.Font Is Nothing) Then
            Me.Font = New Font("Arial", 10.0F, FontStyle.Regular)
        End If
    End Sub
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Handles the <see cref="System.Drawing.Printing.PrintDocument.QueryPageSettings"/> event 
    ''' of the <see cref="PrintDocumentBasic.PrintDocument"/> component.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <param name="sender">
    ''' The source of the event.
    ''' </param>
    ''' 
    ''' <param name="e">
    ''' The <see cref="QueryPageSettingsEventArgs"/> instance containing the event data.
    ''' </param>
    ''' ----------------------------------------------------------------------------------------------------
    <DebuggerStepperBoundary>
    Protected Overridable Sub PrintDocument_QueryPageSettings(ByVal sender As Object, ByVal e As QueryPageSettingsEventArgs) Handles PrintDocument.QueryPageSettings
 
    End Sub
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Handles the <see cref="System.Drawing.Printing.PrintDocument.PrintPage"/> event 
    ''' of the <see cref="PrintDocumentBasic.PrintDocument"/> component.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <param name="sender">
    ''' The source of the event.
    ''' </param>
    ''' 
    ''' <param name="e">
    ''' The <see cref="PrintPageEventArgs"/> instance containing the event data.
    ''' </param>
    ''' ----------------------------------------------------------------------------------------------------
    <DebuggerStepperBoundary>
    Protected Overridable Sub PrintDocument_PrintPage(ByVal sender As Object, ByVal e As PrintPageEventArgs) Handles PrintDocument.PrintPage
 
        ' Page settings.
        Dim brush As New SolidBrush(Me.Color)
        Dim stringFormat As New StringFormat()
        Dim leftMargin As Single = e.MarginBounds.Left
        Dim topMargin As Single = e.MarginBounds.Top
 
        ' Calculate the number of lines per page.
        Dim linesPerPage As Single = (e.MarginBounds.Height / Me.Font.GetHeight(e.Graphics))
 
        ' Iterate over the file, printing each line.
        Dim line As String = Nothing
        Dim count As Integer
        While (count < linesPerPage)
            line = Me.documentStream.ReadLine()
            If (line Is Nothing) Then
                Exit While
            End If
            Dim yPos As Single = (topMargin + count * Me.Font.GetHeight(e.Graphics))
            e.Graphics.DrawString(line, Me.Font, brush, leftMargin, yPos, stringFormat)
            count += 1
        End While
 
        brush.Dispose()
        stringFormat.Dispose()
 
        ' If more lines exist, print another page.
        e.HasMorePages = (line IsNot Nothing)
 
    End Sub
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Handles the <see cref="System.Drawing.Printing.PrintDocument.EndPrint"/> event 
    ''' of the <see cref="PrintDocumentBasic.PrintDocument"/> component.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <param name="sender">
    ''' The source of the event.
    ''' </param>
    ''' 
    ''' <param name="e">
    ''' The <see cref="PrintEventArgs"/> instance containing the event data.
    ''' </param>
    ''' ----------------------------------------------------------------------------------------------------
    <DebuggerStepperBoundary>
    Protected Overridable Sub PrintDocument_EndPrint(ByVal sender As Object, ByVal e As PrintEventArgs) Handles PrintDocument.EndPrint
 
    End Sub
 
#End Region
 
#Region " IDisposable Implementation "
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Flag to detect redundant calls when disposing.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    Private isDisposed As Boolean = False
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Releases all the resources used by this <see cref="PrintDocumentBasic"/> instance.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    <DebuggerStepThrough>
    Public Sub Dispose() Implements IDisposable.Dispose
        Me.Dispose(isDisposing:=True)
        GC.SuppressFinalize(obj:=Me)
    End Sub
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <param name="isDisposing">
    ''' <see langword="True"/>  to release both managed and unmanaged resources; 
    ''' <see langword="False"/> to release only unmanaged resources.
    ''' </param>
    ''' ----------------------------------------------------------------------------------------------------
    <DebuggerStepThrough>
    Protected Overridable Sub Dispose(ByVal isDisposing As Boolean)
 
        If (Not Me.isDisposed) AndAlso (isDisposing) Then
            If (Me.PrintDocument IsNot Nothing) Then
                Me.PrintDocument.Dispose()
                Me.PrintDocument = Nothing
            End If
 
            If (Me.documentStream IsNot Nothing) Then
                Me.documentStream.Close()
                Me.documentStream = Nothing
            End If
 
            If (Me.Font IsNot Nothing) Then
                Me.Font.Dispose()
                Me.Font = Nothing
            End If
 
        End If
 
        Me.isDisposed = True
 
    End Sub
 
#End Region
 
End Class

Using printBasic As New PrintDocumentBasic("C:\Document.txt", Encoding.Default)
    printBasic.PrinterName = ""
    printBasic.Font = New Font("Arial", 10.0F, FontStyle.Regular)
    printBasic.Color = Color.Black
 
    printBasic.Print()
    ' printBasic.CancelPrint()
End Using

''' ----------------------------------------------------------------------------------------------------
''' <summary>
''' Prints a text document.
''' </summary>
''' ----------------------------------------------------------------------------------------------------
''' <seealso cref="IDisposable" />
''' ----------------------------------------------------------------------------------------------------
Public Class PrintDocumentExpert : Implements IDisposable
 
#Region " Private Fields "
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' The <see cref="System.Drawing.Printing.PrintDocument"/> component to print the document.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    Protected WithEvents PrintDocument As PrintDocument
 
#End Region
 
#Region " Properties "
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Gets the document file path.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <value>
    ''' The document file path.
    ''' </value>
    ''' ----------------------------------------------------------------------------------------------------
    Public ReadOnly Property Filepath As String
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Gets or sets the text encoding.
    ''' <para></para>
    ''' If no encoding is specified, the default system encoding will be used.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <value>
    ''' The text encoding.
    ''' </value>
    ''' ----------------------------------------------------------------------------------------------------
    Public Property Encoding As Encoding
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Gets or sets the <see cref="StreamReader"/> instance that encapsulates the document data to be read and printed.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <value>
    ''' The <see cref="StreamReader"/> instance that encapsulates the document data to be read and printed.
    ''' </value>
    ''' ----------------------------------------------------------------------------------------------------
    Public ReadOnly Property DocumentStream As StreamReader
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Gets or sets the <see cref="System.Drawing.Printing.PrinterSettings"/> instance that specifies 
    ''' information about how a document is printed, including the printer that prints it.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <value>
    ''' The <see cref="System.Drawing.Printing.PrinterSettings"/> instance that specifies 
    ''' information about how a document is printed, including the printer that prints it.
    ''' </value>
    ''' ----------------------------------------------------------------------------------------------------
    Public Property PrinterSettings As PrinterSettings
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Gets or sets the <see cref="System.Drawing.Printing.PrintEventHandler"/> delegate method to handle the 
    ''' <see cref="System.Drawing.Printing.PrintDocument.BeginPrint"/> event.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <value>
    ''' The <see cref="System.Drawing.Printing.PrintEventHandler"/> delegate method to handle the 
    ''' <see cref="System.Drawing.Printing.PrintDocument.BeginPrint"/> event.
    ''' </value>
    ''' ----------------------------------------------------------------------------------------------------
    Public Property BeginPrintEventHandler As PrintEventHandler
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Gets or sets the <see cref="System.Drawing.Printing.QueryPageSettingsEventHandler"/> delegate method to handle the 
    ''' <see cref="System.Drawing.Printing.PrintDocument.BeginPrint"/> event.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <value>
    ''' The <see cref="System.Drawing.Printing.PrintEventHandler"/> delegate method to handle the 
    ''' <see cref="System.Drawing.Printing.PrintDocument.QueryPageSettings"/> event.
    ''' </value>
    ''' ----------------------------------------------------------------------------------------------------
    Public Property QueryPageSettingsEventHandler As QueryPageSettingsEventHandler
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Gets or sets the <see cref="System.Drawing.Printing.PrintPageEventHandler"/> delegate method to handle the 
    ''' <see cref="System.Drawing.Printing.PrintDocument.PrintPage"/> event.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <value>
    ''' The <see cref="System.Drawing.Printing.PrintPageEventHandler"/> delegate method to handle the 
    ''' <see cref="System.Drawing.Printing.PrintDocument.PrintPage"/> event.
    ''' </value>
    ''' ----------------------------------------------------------------------------------------------------
    Public Property PrintPageEventHandler As PrintPageEventHandler
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Gets or sets the <see cref="System.Drawing.Printing.PrintEventHandler"/> delegate method to handle the 
    ''' <see cref="System.Drawing.Printing.PrintDocument.BeginPrint"/> event.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <value>
    ''' The <see cref="System.Drawing.Printing.PrintEventHandler"/> delegate method to handle the 
    ''' <see cref="System.Drawing.Printing.PrintDocument.EndPrint"/> event.
    ''' </value>
    ''' ----------------------------------------------------------------------------------------------------
    Public Property EndPrintEventHandler As PrintEventHandler
 
#End Region
 
#Region " Constructors "
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Prevents a default instance of the <see cref="PrintDocumentExpert"/> class from being created.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    <DebuggerNonUserCode>
    Private Sub New()
    End Sub
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Initializes a new instance of the <see cref="PrintDocumentExpert"/> class.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <param name="filepath">
    ''' The document file path.
    ''' </param>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <exception cref="FileNotFoundException">
    ''' </exception>
    ''' ----------------------------------------------------------------------------------------------------
    <DebuggerStepThrough>
    Public Sub New(ByVal filepath As String)
        Me.New(filepath, encoding:=Nothing)
    End Sub
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Initializes a new instance of the <see cref="PrintDocumentExpert"/> class.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <param name="filepath">
    ''' The document file path.
    ''' </param>
    ''' 
    ''' <param name="encoding">
    ''' The text encoding.
    ''' </param>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <exception cref="FileNotFoundException">
    ''' </exception>
    ''' ----------------------------------------------------------------------------------------------------
    <DebuggerStepThrough>
    Public Sub New(ByVal filepath As String, ByVal encoding As Encoding)
        Me.PrintDocument = New PrintDocument() With {
            .DocumentName = filepath
        }
 
        Me.Filepath = filepath
 
        If (encoding Is Nothing) Then
            Me.DocumentStream = New StreamReader(filepath, detectEncodingFromByteOrderMarks:=True)
            Me.Encoding = Me.DocumentStream.CurrentEncoding
        Else
            Me.Encoding = encoding
            Me.DocumentStream = New StreamReader(filepath, encoding, detectEncodingFromByteOrderMarks:=False)
        End If
    End Sub
 
#End Region
 
#Region " Public Methods "
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Prints the current document.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <exception cref="IOException">
    ''' No printer device is installed.
    ''' </exception>
    ''' 
    ''' <exception cref="Exception">
    ''' Printer name is not valid.
    ''' </exception>
    ''' 
    ''' <exception cref="Exception">
    ''' The 'PrintDocumentExpert.PrintPageEventHandler' property must be set before calling the 'PrintDocumentExpert.Print()' method.
    ''' </exception>
    ''' ----------------------------------------------------------------------------------------------------
    <DebuggerStepThrough>
    Public Overridable Sub Print()
 
        If (PrinterSettings.InstalledPrinters.Count = 0) Then
            Throw New IOException("No printer device is installed.")
        End If
 
        If Not String.IsNullOrEmpty(Me.PrinterSettings.PrinterName) AndAlso Not (Me.PrinterSettings.IsValid) Then
            Throw New Exception("Printer name is not valid.")
        End If
 
        If (Me.PrintPageEventHandler Is Nothing) Then
            Throw New Exception("The 'PrintDocumentExpert.PrintPageEventHandler' property must be set before calling the 'PrintDocumentExpert.Print()' method.")
        End If
 
        AddHandler Me.PrintDocument.BeginPrint, Me.BeginPrintEventHandler
        AddHandler Me.PrintDocument.QueryPageSettings, Me.QueryPageSettingsEventHandler
        AddHandler Me.PrintDocument.PrintPage, Me.PrintPageEventHandler
        AddHandler Me.PrintDocument.EndPrint, Me.EndPrintEventHandler
 
        Me.PrintDocument.PrinterSettings = Me.PrinterSettings
        Me.PrintDocument.Print()
 
        RemoveHandler Me.PrintDocument.BeginPrint, Me.BeginPrintEventHandler
        RemoveHandler Me.PrintDocument.QueryPageSettings, Me.QueryPageSettingsEventHandler
        RemoveHandler Me.PrintDocument.PrintPage, Me.PrintPageEventHandler
        RemoveHandler Me.PrintDocument.EndPrint, Me.EndPrintEventHandler
 
    End Sub
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Cancels the print job for the current document.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <exception cref="Exception">
    ''' Print job not found.
    ''' </exception>
    ''' ----------------------------------------------------------------------------------------------------
    <DebuggerStepThrough>
    Public Overridable Sub CancelPrint()
 
        Dim scope As New ManagementScope("root\CIMV2")
        Dim query As New SelectQuery(String.Format("SELECT * FROM Win32_PrintJob WHERE Document = '{0}'", Me.PrintDocument.DocumentName))
        Dim options As New EnumerationOptions With {
                .ReturnImmediately = True,
                .Rewindable = False,
                .DirectRead = True,
                .EnumerateDeep = False
            }
 
        Using mos As New ManagementObjectSearcher(scope, query, options),
              moc As ManagementObjectCollection = mos.Get()
 
            If (moc.Count = 0) Then
                Throw New Exception("Print job not found.")
            End If
 
            For Each mo As ManagementObject In moc
                mo.Delete()
            Next mo
 
        End Using
 
    End Sub
 
#End Region
 
#Region " IDisposable Implementation "
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Flag to detect redundant calls when disposing.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    Private isDisposed As Boolean = False
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Releases all the resources used by this <see cref="PrintDocumentBasic"/> instance.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    <DebuggerStepThrough>
    Public Sub Dispose() Implements IDisposable.Dispose
        Me.Dispose(isDisposing:=True)
        GC.SuppressFinalize(obj:=Me)
    End Sub
 
    ''' ----------------------------------------------------------------------------------------------------
    ''' <summary>
    ''' Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
    ''' </summary>
    ''' ----------------------------------------------------------------------------------------------------
    ''' <param name="isDisposing">
    ''' <see langword="True"/>  to release both managed and unmanaged resources; 
    ''' <see langword="False"/> to release only unmanaged resources.
    ''' </param>
    ''' ----------------------------------------------------------------------------------------------------
    <DebuggerStepThrough>
    Protected Overridable Sub Dispose(ByVal isDisposing As Boolean)
 
        If (Not Me.isDisposed) AndAlso (isDisposing) Then
 
            If (Me.PrintDocument IsNot Nothing) Then
                Me.PrintDocument.Dispose()
                Me.PrintDocument = Nothing
            End If
 
            If (Me.DocumentStream IsNot Nothing) Then
                Me.DocumentStream.Close()
            End If
 
        End If
 
        Me.isDisposed = True
 
    End Sub
 
#End Region
 
End Class

Public Module Module1
 
    Private printExpert As PrintDocumentExpert
 
    Public Sub Main()
 
        printExpert = New PrintDocumentExpert("C:\Document.txt", Encoding.Default)
 
        Using printExpert
            printExpert.PrinterSettings = New PrinterSettings With {
                    .PrinterName = "My Printer Name"
                }
 
            printExpert.BeginPrintEventHandler = AddressOf PrintDocument_BeginPrint
            printExpert.QueryPageSettingsEventHandler = AddressOf PrintDocument_QueryPageSettings
            printExpert.PrintPageEventHandler = AddressOf PrintDocument_PrintPage
            printExpert.EndPrintEventHandler = AddressOf PrintDocument_EndPrint
 
            printExpert.Print()
        End Using
 
    End Sub
 
    Public Sub PrintDocument_BeginPrint(ByVal sender As Object, ByVal e As PrintEventArgs)
    End Sub
 
    Public Sub PrintDocument_QueryPageSettings(ByVal sender As Object, ByVal e As QueryPageSettingsEventArgs)
    End Sub
 
    Public Sub PrintDocument_PrintPage(ByVal sender As Object, ByVal e As PrintPageEventArgs)
        ' Page settings.
        Dim font As New Font("Arial", 10.0F, FontStyle.Regular)
        Dim brush As New SolidBrush(Color.Green)
        Dim stringFormat As New StringFormat()
        Dim leftMargin As Single = e.MarginBounds.Left
        Dim topMargin As Single = e.MarginBounds.Top
 
        ' Calculate the number of lines per page.
        Dim linesPerPage As Single = (e.MarginBounds.Height / font.GetHeight(e.Graphics))
 
        ' Iterate over the file, printing each line.
        Dim line As String = Nothing
        Dim count As Integer
        While (count < linesPerPage)
            line = printExpert.DocumentStream.ReadLine()
            If (line Is Nothing) Then
                Exit While
            End If
            Dim yPos As Single = (topMargin + count * font.GetHeight(e.Graphics))
            e.Graphics.DrawString(line, font, brush, leftMargin, yPos, stringFormat)
            count += 1
        End While
 
        font.Dispose()
        brush.Dispose()
        stringFormat.Dispose()
 
        ' If more lines exist, print another page.
        e.HasMorePages = (line IsNot Nothing)
    End Sub
 
    Public Sub PrintDocument_EndPrint(ByVal sender As Object, ByVal e As PrintEventArgs)
    End Sub
 
End Module

Public Sub Main()
 
    Dim printExpert As PrintDocumentExpert = Nothing
 
    Dim beginPrintEventHandler As PrintEventHandler =
        Sub(ByVal sender As Object, ByVal e As PrintEventArgs)
        End Sub
 
    Dim queryPageSettingsEventHandler As QueryPageSettingsEventHandler =
        Sub(ByVal sender As Object, ByVal e As QueryPageSettingsEventArgs)
        End Sub
 
    Dim printPageEventHandler As PrintPageEventHandler =
    Sub(ByVal sender As Object, ByVal e As PrintPageEventArgs)
        ' Page settings.
        Dim font As New Font("Arial", 10.0F, FontStyle.Regular)
        Dim brush As New SolidBrush(Color.Green)
        Dim stringFormat As New StringFormat()
        Dim leftMargin As Single = e.MarginBounds.Left
        Dim topMargin As Single = e.MarginBounds.Top
 
        ' Calculate the number of lines per page.
        Dim linesPerPage As Single = (e.MarginBounds.Height / font.GetHeight(e.Graphics))
 
        ' Iterate over the file, printing each line.
        Dim line As String = Nothing
        Dim count As Integer
        While (count < linesPerPage)
            line = printExpert.DocumentStream.ReadLine()
            If (line Is Nothing) Then
                Exit While
            End If
            Dim yPos As Single = (topMargin + count * font.GetHeight(e.Graphics))
            e.Graphics.DrawString(line, font, brush, leftMargin, yPos, stringFormat)
            count += 1
        End While
 
        font.Dispose()
        brush.Dispose()
        stringFormat.Dispose()
 
        ' If more lines exist, print another page.
        e.HasMorePages = (line IsNot Nothing)
    End Sub
 
    Dim endPrintEventHandler As PrintEventHandler =
        Sub(ByVal sender As Object, ByVal e As PrintEventArgs)
        End Sub
 
    printExpert = New PrintDocumentExpert("C:\Document.txt", Encoding.Default)
    Using printExpert
        printExpert.PrinterSettings = New PrinterSettings With {
            .PrinterName = "My Printer Name"
        }
 
        printExpert.BeginPrintEventHandler = beginPrintEventHandler
        printExpert.QueryPageSettingsEventHandler = queryPageSettingsEventHandler
        printExpert.PrintPageEventHandler = printPageEventHandler
        printExpert.EndPrintEventHandler = endPrintEventHandler
 
        printExpert.Print()
    End Using
 
End Sub

• https://foro.elhacker.net/net/sourcecode_fhm_crawler_freehardmusiccom-t482152.0.html

#Region " Imports "
 
Imports System.Collections.ObjectModel
 
#End Region
 
Namespace FHM
 
    ''' <summary>Represents the information of an album crawled with <see cref="FHM.Crawler"/>.</summary>
    Public NotInheritable Class AlbumInfo
 
#Region " Properties "
 
        ''' <summary>Gets the album identifier (that is used in the 'sobiid' and 'sobi2id' parameters).</summary>
        Public ReadOnly Property Id As String
 
        ''' <summary>Gets the album <see cref="Uri"/>.</summary>
        Public ReadOnly Property Uri As Uri
 
        ''' <summary>Gets the artist name.</summary>
        Public ReadOnly Property Artist As String
 
        ''' <summary>Gets the album title.</summary>
        Public ReadOnly Property Title As String
 
        ''' <summary>Gets the country of the band/artist.</summary>
        Public ReadOnly Property Country As String
 
        ''' <summary>Gets the music genre.</summary>
        Public ReadOnly Property Genre As String
 
        ''' <summary>Gets the year that the album has been released.</summary>
        Public ReadOnly Property Year As Integer
 
        ''' <summary>Gets the urls to download the album. It can be a single url, or multiple of them.</summary>
        Public ReadOnly Property DownloadLinks As ReadOnlyCollection(Of String)
 
#End Region
 
#Region " Constructors "
 
        Private Sub New()
        End Sub
 
        ''' <summary>Initializes a new instance of the <see cref="AlbumInfo"/> class.</summary>
        ''' <param name="id">The album identifier>.</param>
        ''' <param name="uri">The album <see cref="Uri"/>.</param>
        ''' <param name="artist">The artist name.</param>
        ''' <param name="title">The album title.</param>
        ''' <param name="country">The country of the band/artist.</param>
        ''' <param name="genre">The music genre.</param>
        ''' <param name="year">The year that the album has been released.</param>
        ''' <param name="downloadLinks">The urls to download the album. It can be a single url, or multiple of them.</param>
        Public Sub New(id As String, uri As Uri,
                       artist As String, title As String,
                       country As String, genre As String, year As Integer,
                       downloadLinks As IEnumerable(Of String))
 
            Me.Id = id
            Me.Uri = uri
            Me.Artist = artist
            Me.Title = title
            Me.Country = country
            Me.Genre = genre
            Me.Year = year
            Me.DownloadLinks = New ReadOnlyCollection(Of String)(downloadLinks)
 
        End Sub
 
#End Region
 
    End Class
 
End Namespace

#Region " Imports "
 
Imports System.Collections.Specialized
 
Imports ElektroKit.Core.Extensions.NameValueCollection
 
#End Region
 
Namespace FHM
 
    ''' <summary>Represents a search query of the http://freehardmusic.com/ website, 
    ''' that is managed by the <see cref="FHM.Crawler.FetchAlbums()"/> 
    ''' and <see cref="FHM.Crawler.FetchAlbumsAsync()"/> methods.
    ''' <para></para>
    ''' Note that a search query can be performed in two different ways:
    ''' <para></para> 
    ''' 1. An artist-name based search (<see cref="SearchQuery.Artist"/>).
    ''' <para></para> 
    ''' 2. A non-artist name based search. That is, a custom search based on country (<see cref="SearchQuery.Country"/>), 
    ''' genre (<see cref="SearchQuery.Genre"/>) or year criterias (<see cref="SearchQuery.Year"/>); 
    ''' this kind of search can combine the three mentioned criterias, but not the artist name (<see cref="SearchQuery.Artist"/>).
    Public NotInheritable Class SearchQuery
 
#Region " Properties "
 
        ''' <summary>Gets or sets the artist name.</summary>
        Public Property Artist As String
            Get
                Return Me.artistB
            End Get
            <DebuggerStepThrough>
            Set(value As String)
                If Not (Me.countryB.Equals("all", StringComparison.OrdinalIgnoreCase)) OrElse
                   Not (Me.genreB.Equals("all", StringComparison.OrdinalIgnoreCase)) OrElse
                   Not (Me.yearB.Equals("all", StringComparison.OrdinalIgnoreCase)) Then
 
                    Throw New ArgumentException("To perform an artist-name based search, you must set the value of Country, Genre and Year properties to ""all"" before setting the Artist property.", paramName:=NameOf(value))
                End If
                Me.artistB = value
            End Set
        End Property
        Private artistB As String
 
        ''' <summary>Gets or sets the country of the band/artist.</summary>
        Public Property Country As String
            Get
                Return Me.countryB
            End Get
            <DebuggerStepThrough>
            Set(value As String)
                If Not (value.Equals("all", StringComparison.OrdinalIgnoreCase)) AndAlso Not String.IsNullOrEmpty(Me.artistB) Then
                    Throw New ArgumentException("To perform a country based search, you must set the value of Artist property to an empty string.", paramName:=NameOf(value))
                End If
                Me.countryB = value
            End Set
        End Property
        Private countryB As String
 
        ''' <summary>Gets or sets the music genre.</summary>
        Public Property Genre As String
            Get
                Return Me.genreB
            End Get
            <DebuggerStepThrough>
            Set(value As String)
                If Not (value.Equals("all", StringComparison.OrdinalIgnoreCase)) AndAlso Not String.IsNullOrEmpty(Me.artistB) Then
                    Throw New ArgumentException("To perform a genre based search, you must set the value of Artist property to an empty string.", paramName:=NameOf(value))
                End If
                Me.genreB = value
            End Set
        End Property
        Private genreB As String
 
        ''' <summary>Gets or sets the year that the album has been released.</summary>
        Public Property Year As String
            Get
                Return Me.yearB
            End Get
            <DebuggerStepThrough>
            Set(value As String)
                If Not (value.Equals("all", StringComparison.OrdinalIgnoreCase)) AndAlso Not String.IsNullOrEmpty(Me.artistB) Then
                    Throw New ArgumentException("To perform a year based search, you must set the value of Artist property to an empty string.", paramName:=NameOf(value))
                End If
                Me.yearB = value
            End Set
        End Property
        Private yearB As String
 
        ''' <summary>Gets the <see cref="Uri"/> that represents this search query.</summary>
        Public ReadOnly Property Uri As Uri
            Get
                Return Me.Uri(searchPage:=0)
            End Get
        End Property
 
        ''' <summary>Gets the <see cref="Uri"/> that represents this search query.</summary>
        ''' <param name="searchPage">The index of the search page parameter.</param>
        Public ReadOnly Property Uri(searchPage As Integer) As Uri
            Get
                Return New Uri(Me.ToString(searchPage), UriKind.Absolute)
            End Get
        End Property
 
#End Region
 
#Region " Constructors "
 
        Private Sub New()
        End Sub
 
        ''' <summary>Initializes a new instance of the <see cref="SearchQuery"/> class.</summary>
        ''' <param name="artist">The artist name.</param>
        Public Sub New(artist As String)
            Me.artistB = artist
            Me.genreB = "all"
            Me.countryB = "all"
            Me.yearB = "all"
        End Sub
 
        ''' <summary>Initializes a new instance of the <see cref="SearchQuery"/> class.</summary>
        ''' <param name="genre">The music genre. Default value is: "all"</param>
        ''' <param name="country">The country of the band/artist. Default value is: "all"</param>
        ''' <param name="year">The year that the album has been released. Default value is: "all"</param>
        Public Sub New(Optional genre As String = "all",
                       Optional country As String = "all",
                       Optional year As String = "all")
 
            Me.artistB = ""
            Me.genreB = genre
            Me.countryB = country
            Me.yearB = year
        End Sub
 
#End Region
 
#Region " Public Methods "
 
        ''' <summary>Resets the current search query to its default values.</summary>
        <DebuggerStepThrough>
        Public Sub Reset()
            Me.Artist = ""
            Me.Country = "all"
            Me.Genre = "all"
            Me.Year = "all"
        End Sub
 
        ''' <summary>Returns a <see cref="String"/> that represents the search query.</summary>
        ''' <returns>A <see cref="String"/> that represents the search query.</returns>
        Public Overrides Function ToString() As String
            Return Me.ToString(searchPage:=0)
        End Function
 
        ''' <summary>Returns a <see cref="String"/> that represents the search query.</summary>
        ''' <param name="searchPage">The index of the search page parameter.</param>
        ''' <returns>A <see cref="String"/> that represents the search query.</returns>
        Public Overloads Function ToString(searchPage As Integer) As String
 
            If (searchPage < 0) Then
                Throw New ArgumentException("Positive integer value is required.", paramName:=NameOf(searchPage))
            End If
 
            Dim params As New NameValueCollection From {
                {"field_band", Me.Artist},
                {"field_country", Me.Country},
                {"field_genre", Me.Genre},
                {"field_year", Me.Year},
                {"option", "com_sobi2"},
                {"search", "Search"},
                {"searchphrase", "exact"},
                {"sobi2Search", ""},
                {"sobi2Task", "axSearch"},
                {"SobiCatSelected_0", "0"},
                {"sobiCid", "0"},
                {"SobiSearchPage", searchPage}
            }
 
            Return params.ToQueryString(New Uri("http://freehardmusic.com/index.php"))
 
        End Function
 
#End Region
 
    End Class
 
End Namespace

Namespace FHM
 
    ''' <summary>Represents the event data of the <see cref="FHM.Crawler.PageCrawlBegin"/> event.</summary>
    Public NotInheritable Class PageCrawlBeginEventArgs : Inherits EventArgs
 
#Region " Properties "
 
        ''' <summary>Gets the search query used.</summary>
        Public ReadOnly Property SearchQuery As SearchQuery
 
        ''' <summary>Gets the index of the search page being crawled.</summary>
        Public ReadOnly Property SearchPage As Integer
 
#End Region
 
#Region " Constructors "
 
        Private Sub New()
        End Sub
 
        ''' <summary>Initializes a new instance of the <see cref="PageCrawlBeginEventArgs"/> class.</summary>
        ''' <param name="searchQuery">The search query used.</param>
        ''' <param name="searchPage">The index of the search page.</param>
        Public Sub New(searchQuery As SearchQuery, searchPage As Integer)
            Me.SearchQuery = searchQuery
            Me.SearchPage = searchPage
        End Sub
 
#End Region
 
    End Class
 
End Namespace

Namespace FHM
 
    ''' <summary>Represents the event data of the <see cref="FHM.Crawler.PageCrawlEnd"/> event.</summary>
    Public NotInheritable Class PageCrawlEndEventArgs : Inherits EventArgs
 
#Region " Properties "
 
        ''' <summary>Gets the search query used.</summary>
        Public ReadOnly Property SearchQuery As SearchQuery
 
        ''' <summary>Gets the index of the search page crawled.</summary>
        Public ReadOnly Property SearchPage As Integer
 
        ''' <summary>Gets a collection of <see cref="AlbumInfo"/> that contains the information of the albums that were crawled.</summary>
        Public ReadOnly Property Albums As ReadOnlyCollection(Of AlbumInfo)
 
#End Region
 
#Region " Constructors "
 
        Private Sub New()
        End Sub
 
        ''' <summary>Initializes a new instance of the <see cref="PageCrawlEndEventArgs"/> class.</summary>
        ''' <param name="searchQuery">The search query used.</param>
        ''' <param name="searchPage">The index of the search page crawled.</param>
        ''' <param name="albums">A collection of <see cref="AlbumInfo"/> that contains the information of the albums that were crawled.</param>
        Public Sub New(searchQuery As SearchQuery, searchPage As Integer, albums As ICollection(Of AlbumInfo))
            Me.SearchQuery = searchQuery
            Me.SearchPage = searchPage
            Me.Albums = New ReadOnlyCollection(Of AlbumInfo)(albums)
        End Sub
 
#End Region
 
    End Class
 
End Namespace

#Region " Imports "
 
Imports System.Collections.Specialized
Imports System.Text.RegularExpressions
 
Imports HtmlDocument = HtmlAgilityPack.HtmlDocument
Imports HtmlNode = HtmlAgilityPack.HtmlNode
Imports HtmlNodeCollection = HtmlAgilityPack.HtmlNodeCollection
 
Imports ElektroKit.Core.Extensions.NameValueCollection
 
#End Region
 
Namespace FHM
 
    ''' <summary>A crawler that searchs and collect albums (its download links) from the http://freehardmusic.com/ website.</summary>
    Public Class Crawler : Implements IDisposable
 
#Region " Private Fields "
 
        ''' <summary>The <see cref="Uri"/> that points to "http://freehardmusic.com/".</summary>
        Protected ReadOnly uriBase As New Uri("http://freehardmusic.com/")
 
        ''' <summary>The <see cref="Uri"/> that points to "http://freehardmusic.com/index2.php".</summary>
        Protected ReadOnly uriIndex As New Uri(Me.uriBase, "/index2.php")
 
        ''' <summary>Flag that determines whether this <see cref="Crawler"/> is busy in a pending fetch operation.</summary>
        Protected isFetching As Boolean
 
        ''' <summary>The <see cref="CancellationToken"/> instance that cancels a pending fetch operation 
        ''' started by a call of <see cref="Crawler.FetchAlbumsAsync()"/>.</summary>
        Protected cancelToken As CancellationToken
 
        ''' <summary>The <see cref="CancellationTokenSource"/> instance that signals to <see cref="Crawler.cancelToken"/>.</summary>
        Protected cancelTokenSrc As CancellationTokenSource
 
#End Region
 
#Region " Properties "
 
        ''' <summary>Gets the search query.</summary>
        Public ReadOnly Property SearchQuery As SearchQuery
 
#End Region
 
#Region " Events "
 
        ''' <summary>Occurs when a page is about to be crawled.</summary>
        Public Event PageCrawlBegin As EventHandler(Of PageCrawlBeginEventArgs)
 
        ''' <summary>Occurs when a page is crawled.</summary>
        Public Event PageCrawlEnd As EventHandler(Of PageCrawlEndEventArgs)
 
#End Region
 
#Region " Constructors "
 
        ''' <summary>Initializes a new instance of the <see cref="Crawler"/> class.</summary>
        Public Sub New()
            Me.SearchQuery = New SearchQuery()
            Me.cancelTokenSrc = New CancellationTokenSource()
            Me.cancelToken = Me.cancelTokenSrc.Token
        End Sub
 
#End Region
 
#Region " Public Methods "
 
        ''' <summary>Gets the count of the albums found using the current search query.</summary>
        ''' <returns>The count of the albums found using the current search query.</returns>
        <DebuggerStepThrough>
        Public Overridable Function GetAlbumCount() As Integer
            Dim t As Task(Of Integer) = Task.Run(Of Integer)(AddressOf Me.GetAlbumCountAsync)
            t.Wait()
 
            Return t.Result
        End Function
 
        ''' <summary>Asynchronously gets the count of the albums found using the current search query.</summary>
        ''' <returns>The count of the albums found using the current search query.</returns>
        <DebuggerStepThrough>
        Public Overridable Async Function GetAlbumCountAsync() As Task(Of Integer)
            Dim query As String = Me.SearchQuery.ToString(searchPage:=0)
            Dim uriSearch As New Uri(query)
            Dim htmlSourceCode As String = String.Empty
            Using wc As New WebClient
                htmlSourceCode = Await wc.DownloadStringTaskAsync(uriSearch)
            End Using
 
            Dim htmldoc As New HtmlDocument
            htmldoc.LoadHtml(htmlSourceCode)
 
            Dim xPathResultString As String = "//div[@id='mainbody']/table[1]/tr[2]/td"
 
            Dim node As HtmlNode = htmldoc.DocumentNode.SelectSingleNode(xPathResultString)
 
            Dim text As String = node.InnerText
            text = Regex.Replace(text, "\n", "", RegexOptions.None)    ' Remove new lines.
            text = Regex.Replace(text, "\t", " "c, RegexOptions.None)  ' Replace tabs for white-spaces.
            text = Regex.Replace(text, "\s+", " "c, RegexOptions.None) ' Replace duplicated white-spaces.
 
            Dim albumCount As Integer = CInt(Regex.Match(text, "\d+", RegexOptions.None).Value)
            Return albumCount
        End Function
 
        ''' <summary>Fetch any album found using the current search query.</summary>
        <DebuggerStepThrough>
        Public Overridable Sub FetchAlbums()
            Dim t As Task = Task.Run(AddressOf Me.FetchAlbumsAsync)
            t.Wait()
        End Sub
 
        ''' <summary>Asynchronously fetch any album found using the current search query.</summary>
        ''' <returns>Returns <see langword="False"/> if the fetch operation was canceled by a call to 
        ''' <see cref="Crawler.CancelFetchAlbumsAsync()"/> method.</returns>
        <DebuggerStepThrough>
        Public Overridable Async Function FetchAlbumsAsync() As Task(Of Boolean)
            If (Me.isFetching) Then
                Throw New Exception("Another fetch operation is already running in background.")
            End If
            Me.isFetching = True
 
            Me.cancelTokenSrc.Dispose()
            Me.cancelTokenSrc = New CancellationTokenSource()
            Me.cancelToken = Me.cancelTokenSrc.Token
 
            Dim albumCount As Integer = Await Me.GetAlbumCountAsync()
            If (albumCount = 0) Then
                Me.isFetching = False
                Return True
            End If
 
            Dim maxPages As Integer = ((albumCount \ 10) + 1) ' 10 albums per page.
            For i As Integer = 0 To (maxPages - 1)
                Dim query As String = Me.SearchQuery.ToString(searchPage:=i)
                Dim uriSearch As New Uri(query)
                Dim htmlSourceCode As String = String.Empty
                Using wc As New WebClient
                    htmlSourceCode = Await wc.DownloadStringTaskAsync(uriSearch)
                End Using
 
                If (Me.cancelToken.IsCancellationRequested) Then
                    Me.isFetching = False
                    Return False
                End If
 
                Me.OnPageCrawlBegin(New PageCrawlBeginEventArgs(Me.SearchQuery, i))
                Await Me.ParseHtmlSourceCode(i, htmlSourceCode)
            Next i
 
            Me.isFetching = False
            Return True
        End Function
 
        ''' <summary>Aborts a pending fetch operation started by a call to <see cref="Crawler.FetchAlbumsAsync()"/> function.</summary>
        <DebuggerStepThrough>
        Public Sub CancelFetchAlbumsAsync()
            If Not (Me.isFetching) Then
                Throw New Exception("No fetch operation is running.")
            End If
 
            If (Me.cancelToken.IsCancellationRequested) Then
                ' Handle redundant cancellation calls to CancelFetchAlbums()...
                Me.cancelToken.ThrowIfCancellationRequested()
            End If
 
            Me.cancelTokenSrc.Cancel()
        End Sub
 
        ''' <summary>Resets the current search query (<see cref="Crawler.SearchQuery"/>) to its default values.</summary>
        <DebuggerStepThrough>
        Public Sub ResetSearchQuery()
            Me.SearchQuery.Reset()
        End Sub
 
#End Region
 
#Region " Event-Invocators "
 
        ''' <summary>Raises the <see cref="Crawler.PageCrawlBegin"/> event.</summary>
        ''' <param name="e">The <see cref="PageCrawlBeginEventArgs"/> instance containing the event data.</param>
        Protected Overridable Sub OnPageCrawlBegin(e As PageCrawlBeginEventArgs)
            If (Me.PageCrawlBeginEvent IsNot Nothing) Then
                RaiseEvent PageCrawlBegin(Me, e)
            End If
        End Sub
 
        ''' <summary>Raises the <see cref="Crawler.PageCrawlEnd"/> event.</summary>
        ''' <param name="e">The <see cref="PageCrawlBeginEventArgs"/> instance containing the event data.</param>
        Protected Overridable Sub OnPageCrawlEnd(e As PageCrawlEndEventArgs)
            If (Me.PageCrawlEndEvent IsNot Nothing) Then
                RaiseEvent PageCrawlEnd(Me, e)
            End If
        End Sub
 
#End Region
 
#Region " Private Methods "
 
        ''' <summary>Parses the html source code to crawl the albums.</summary>
        ''' <param name="searchPage">The index of the search page.</param>
        ''' <param name="htmlSourceCode">The html source code to parse.</param>
        ''' <returns>Returns <see langword="True"/> if the operation succed; otherwise, <see langword="False"/>.</returns>
        <DebuggerStepperBoundary>
        Private Async Function ParseHtmlSourceCode(searchPage As Integer, htmlSourceCode As String) As Task(Of Boolean)
 
            Dim albums As New Collection(Of AlbumInfo)
 
            Dim xPathTable As String = "//table[@class='vicard']"
            Dim xPathArtist As String = ".//tr/td/span[@class='sobi2Listing_field_band']"
            Dim xPathCountry As String = ".//table[@class='vicard2']/tr/td[@class='goods']/table[@class='goods']/tr/td/img"
            Dim xPathGenre As String = ".//tr[3]/td/table/tr/td[2]/table/tr/td"
            Dim xPathYear As String = ".//tr/td/span[@class='sobi2Listing_field_year']"
            Dim xPathTitle As String = ".//tr/td/p[@class='sobi2ItemTitle']/a[@title]"
            Dim xPathUrl As String = ".//table[@class='vicard2']/tr/td/a[@href]"
 
            Dim htmldoc As New HtmlDocument
            Try
              htmldoc.LoadHtml(htmlSourceCode)
            Catch ex As Exception
                Return False
            End Try
 
            Dim nodes As HtmlNodeCollection = htmldoc.DocumentNode.SelectNodes(xPathTable)
            If (nodes.Count = 0) Then
                Return False
            End If
 
            For Each node As HtmlNode In nodes
                Dim artist As String
                Dim title As String
                Dim country As String
                Dim genre As String
                Dim year As String
 
                Dim albumId As String
                Dim albumUrl As String
 
                Try
                    artist = node.SelectSingleNode(xPathArtist).InnerText
                    artist = Encoding.UTF8.GetString(Encoding.Default.GetBytes(artist))
                    artist = HttpUtility.HtmlDecode(artist)
                    artist = New CultureInfo("en-US").TextInfo.ToTitleCase(artist.Trim(" "c).ToLower())
                Catch ex As Exception
                    artist = "unknown"
                End Try
 
                Try
                    title = node.SelectSingleNode(xPathTitle).GetAttributeValue("title", "")
                    title = Encoding.UTF8.GetString(Encoding.Default.GetBytes(title))
                    title = HttpUtility.HtmlDecode(title)
                    title = New CultureInfo("en-US").TextInfo.ToTitleCase(title.Trim(" "c).ToLower())
                Catch ex As Exception
                    title = "unknown"
                End Try
 
                Try
                    country = node.SelectSingleNode(xPathCountry).GetAttributeValue("src", "unknown")
                    country = Path.GetFileNameWithoutExtension(country)
                    country = New CultureInfo("en-US").TextInfo.ToTitleCase(country.ToLower())
                Catch ex As Exception
                    country = "unknown"
                End Try
 
                Try
                    genre = node.SelectSingleNode(xPathGenre).InnerText
                    genre = Regex.Replace(genre, "\n", "", RegexOptions.None)    ' Remove new lines.
                    genre = Regex.Replace(genre, "\t", " "c, RegexOptions.None)  ' Replace tabs for white-spaces.
                    genre = Regex.Replace(genre, "\s+", " "c, RegexOptions.None) ' Replace duplicated white-spaces.
                    genre = New CultureInfo("en-US").TextInfo.ToTitleCase(genre.Trim(" "c).ToLower())
                Catch ex As Exception
                    genre = "unknown"
                End Try
 
                Try
                    year = node.SelectSingleNode(xPathYear).InnerText.Trim(" "c)
                Catch ex As Exception
                    year = "unknown"
                End Try
 
                Try
                    albumUrl = node.SelectSingleNode(xPathUrl).GetAttributeValue("href", "").Trim(" "c)
                    albumUrl = HttpUtility.HtmlDecode(albumUrl)
                Catch ex As Exception
                    Continue For
                End Try
 
                albumId = HttpUtility.ParseQueryString(New Uri(albumUrl).Query)("sobi2Id")
 
                Dim downloadUrlParams As New NameValueCollection From {
                    {"sobiid", albumId},
                    {"sobi2Task", "addSRev"},
                    {"no_html", "1"},
                    {"option", "com_sobi2"},
                    {"rvote", "1"}
                }
 
                Dim downloadLinks As List(Of String)
                Try
                    Using wc As New WebClient()
                        htmlSourceCode = Await wc.DownloadStringTaskAsync(New Uri(downloadUrlParams.ToQueryString(Me.uriIndex)))
                    End Using
 
                    Dim xDoc As XDocument = XDocument.Parse(htmlSourceCode)
                    Dim elements As IEnumerable(Of XElement) = xDoc.<rev>
                    downloadLinks = New List(Of String) From {
                        elements.<msg>.Value,
                        elements.<msg2>.Value,
                        elements.<msg3>.Value,
                        elements.<msg4>.Value,
                        elements.<msg5>.Value,
                        elements.<msg6>.Value,
                        elements.<msg7>.Value,
                        elements.<msg8>.Value,
                        elements.<msg9>.Value,
                        elements.<msg10>.Value,
                        elements.<msg11>.Value,
                        elements.<msg12>.Value,
                        elements.<msg13>.Value
                    }
                Catch ex As Exception
                    Continue For
                End Try
 
                downloadLinks = (From item As String In downloadLinks
                                 Where Not String.IsNullOrWhiteSpace(item)
                                 Select item.TrimEnd(" "c)
                                ).ToList()
 
                Dim albumInfo As New AlbumInfo(albumId, New Uri(albumUrl, UriKind.Absolute),
                                               artist, title, country, genre, year,
                                               downloadLinks)
 
                albums.Add(albumInfo)
            Next node
 
            Me.OnPageCrawlEnd(New PageCrawlEndEventArgs(Me.SearchQuery, searchPage, albums))
            Return True
        End Function
 
#End Region
 
#Region " IDisposable Implementation "
 
        ''' <summary>Flag to detect redundant calls when disposing.</summary>
        Private isDisposed As Boolean = False
 
        ''' <summary>Releases all the resources used by this <see cref="Crawler"/>.</summary>
        <DebuggerStepThrough>
        Public Sub Dispose() Implements IDisposable.Dispose
            Me.Dispose(isDisposing:=True)
            GC.SuppressFinalize(obj:=Me)
        End Sub
 
        ''' <summary>Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.</summary>
        ''' <param name="isDisposing"><see langword="True"/> to release both managed and unmanaged resources; 
        ''' <see langword="False"/> to release only unmanaged resources.</param>
        <DebuggerStepThrough>
        Protected Overridable Sub Dispose(isDisposing As Boolean)
            If (Not Me.isDisposed) AndAlso (isDisposing) Then
                If (Me.cancelTokenSrc IsNot Nothing) Then
                    Me.cancelTokenSrc.Dispose()
                    Me.cancelTokenSrc = Nothing
                End If
                Me.cancelToken = Nothing
                Me.isFetching = False
                Me.ResetSearchQuery()
            End If
 
            Me.isDisposed = True
        End Sub
 
#End Region
 
    End Class
 
End Namespace