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En una variable de este tipo como puedo forzar que tenga solo la cantidad de numeros que yo quiera,

 era antes mas o menos

Dim Name As String * 30   

pero ya no vale para net

tengo este codigo para hacerlo de longitud fija

  Dim Results As IEnumerable(Of Integer) =
          (
              From Value As Integer
                In (Result).Distinct Where (Value <= MAX))
 
 
        ListBox6.Items.AddRange(Results.Cast(Of Object).ToArray)

Luis

en .NET el equivalente es:

<VBFixedString(30)> Dim vVariable As String
 
    Dim MyFixedLengthString As New VB6.FixedLengthString(30)

aca lo explican:

Preparing Your Visual Basic 6.0 Applications for the Upgrade to Visual Basic .NET (https://msdn.microsoft.com/en-us/library/aa260644%28VS.60%29.aspx#vb6tovbdotnet_arrays)

igualmente no lo recomiendan.

 gracias seba123neo

Lo mirare y si no me vale tratare en la funcion que me restrinja las cantidades :)

luis

Si lo que quieres es limitar la cantidad de caracteres de un String, puedes utilizar el buffer de un StringBuilder:

Dim sb As New StringBuilder(1, 5) ' máximo 5 caracteres.
sb.Append("123456") ' 6 caracteres, dará error por sobrepasar el límite.

Si lo que quieres es un String de longitud variable pero que en principio contenga un número específico de caracteres, puedes usar el constructor del datatype String:

Dim str As New String(" "c, 10)

Si lo que quieres es crear un string de longitud fija, siempre puedes crear tu propia extensión de método, o type:

Modo de empleo:

Dim fixedStr As FixedLengthString
 
fixedStr = New FixedLengthString("", 10)
MessageBox.Show("""" & fixedStr.ValueFixed & """") ' Result: "          "
 
fixedStr.ValueUnfixed = "12345"
MessageBox.Show("""" & fixedStr.ValueFixed & """") ' Result: "1245      "
 
fixedStr.ValueUnfixed = "1234567890abc"
MessageBox.Show("""" & fixedStr.ValueFixed & """") ' Result: "1234567890"

Source:

' ***********************************************************************
' Author   : Elektro
' Modified : 04-February-2015
' ***********************************************************************
' <copyright file="FixedLengthString.vb" company="Elektro Studios">
'     Copyright (c) Elektro Studios. All rights reserved.
' </copyright>
' ***********************************************************************
 
''' <summary>
''' Defines a <see cref="String"/> with a fixed length.
''' </summary>
Public NotInheritable Class FixedLengthString
 
#Region " Properties "
 
    ''' <summary>
    ''' Gets or sets the fixed string length.
    ''' </summary>
    ''' <value>The fixed string length.</value>
    Public Property FixedLength As Integer
        Get
            Return Me.fixedLength1
        End Get
        Set(ByVal value As Integer)
            Me.fixedLength1 = value
        End Set
    End Property
    ''' <summary>
    ''' The fixed string length.
    ''' </summary>
    Private fixedLength1 As Integer
 
    ''' <summary>
    ''' Gets or sets the padding character thath fills the string.
    ''' </summary>
    ''' <value>The padding character thath fills the string.</value>
    Public Property PaddingChar As Char
        Get
            Return Me.paddingChar1
        End Get
        Set(ByVal value As Char)
            Me.paddingChar1 = value
        End Set
    End Property
    ''' <summary>
    ''' The padding character thath fills the string.
    ''' </summary>
    Private paddingChar1 As Char
 
    ''' <summary>
    ''' Gets or sets the unmodified string.
    ''' </summary>
    ''' <value>The unmodified string.</value>
    Public Property ValueUnfixed As String
        Get
            Return Me.valueUnfixed1
        End Get
        Set(ByVal value As String)
            Me.valueUnfixed1 = value
        End Set
    End Property
    ''' <summary>
    ''' The unmodified string.
    ''' </summary>
    Private valueUnfixed1 As String
 
    ''' <summary>
    ''' Gets the fixed string.
    ''' </summary>
    ''' <value>The fixed string.</value>
    Public ReadOnly Property ValueFixed As String
        Get
            Return Me.FixLength(Me.valueUnfixed1, Me.fixedLength1, Me.paddingChar1)
        End Get
    End Property
 
#End Region
 
#Region " Constructors "
 
    ''' <summary>
    ''' Prevents a default instance of the <see cref="FixedLengthString" /> class from being created.
    ''' </summary>
    Private Sub New()
    End Sub
 
    ''' <summary>
    ''' Initializes a new instance of the <see cref="FixedLengthString" /> class.
    ''' </summary>
    ''' <param name="value">The string value.</param>
    ''' <param name="fixedLength">The fixed string length.</param>
    ''' <param name="paddingChar">The padding character thath fills the string.</param>
    Public Sub New(ByVal value As String,
                   ByVal fixedLength As Integer,
                   Optional ByVal paddingChar As Char = " "c)
 
        Me.valueUnfixed1 = value
        Me.fixedLength1 = fixedLength
        Me.paddingChar1 = paddingChar
 
    End Sub
 
#End Region
 
#Region " Public Methods "
 
    ''' <summary>
    ''' Returns a <see cref="System.String" /> that represents this instance.
    ''' </summary>
    ''' <returns>A <see cref="System.String" /> that represents this instance.</returns>
    Public Overrides Function ToString() As String
        Return Me.ValueFixed
    End Function
 
#End Region
 
#Region " Private Methods "
 
    ''' <summary>
    ''' Fixes the length of the specified string.
    ''' </summary>
    ''' <param name="value">The string value.</param>
    ''' <param name="fixedLength">The fixed string length.</param>
    ''' <param name="paddingChar">The padding character thath fills the string.</param>
    ''' <returns>System.String.</returns>
    Private Function FixLength(ByVal value As String,
                               ByVal fixedLength As Integer,
                               ByVal paddingChar As Char) As String
 
        If (value.Length > fixedLength) Then
            Return value.Substring(0, fixedLength)
        Else
            Return value.PadRight(fixedLength, paddingChar)
        End If
 
    End Function
 
#End Region
 
End Class