Dim col1 As IEnumerable(Of Integer) = {1, 5, 6, 7, 8, 9, 10, 11}
Dim col2 As IEnumerable(Of Integer) = {1, 5, 6, 7, 8, 9, 10, 11}
Dim col3 As IEnumerable(Of Integer) = {1, 2, 8, 6, 9}
Dim col4 As IEnumerable(Of Integer) = {2, 2, 3}
Dim max As Integer = 10
 
Dim cols As IEnumerable(Of IEnumerable(Of String)) =
    From col As IEnumerable(Of Integer) In {col1, col2, col3, col4}
    Group By String.Join("", col).AsEnumerable
    Into Group
    Select From value As Integer In Group.First.Distinct
           Where Not (value > max)
           Select value.ToString(format:="0#")
 
ListBox1.Items.AddRange((From col As IEnumerable(Of String) In cols Select String.Join(", ", col)).ToArray)

01, 05, 06, 07, 08, 09, 10
01, 02, 08, 06, 09
02, 03

    ''' <remarks>
    ''' *****************************************************************
    ''' Snippet Title: Overlay Images
    ''' Code's author: Elektro
    ''' Date Modified: 30-April-2015
    ''' *****************************************************************
    ''' </remarks>
    ''' <summary>
    ''' Overlay an image over a background image.
    ''' </summary>
    ''' <param name="backImage">The background image.</param>
    ''' <param name="topImage">The topmost image.</param>
    ''' <param name="topPosX">An optional adjustment of the top image's "X" position.</param>
    ''' <param name="topPosY">An optional adjustment of the top image's "Y" position.</param>
    ''' <returns>The overlayed image.</returns>
    ''' <exception cref="ArgumentNullException">backImage or topImage</exception>
    ''' <exception cref="ArgumentException">Image bounds are greater than background image.;topImage</exception>
    Public Shared Function OverlayImages(ByVal backImage As Image,
                                         ByVal topImage As Image,
                                         Optional ByVal topPosX As Integer = 0,
                                         Optional ByVal topPosY As Integer = 0) As Image
 
        If backImage Is Nothing Then
            Throw New ArgumentNullException(paramName:="backImage")
 
        ElseIf topImage Is Nothing Then
            Throw New ArgumentNullException(paramName:="topImage")
 
        ElseIf (topImage.Width > backImage.Width) OrElse
               (topImage.Height > backImage.Height) Then
            Throw New ArgumentException(message:="Image bounds are greater than background image.", paramName:="topImage")
 
        Else
            topPosX += CInt((backImage.Width / 2) - (topImage.Width / 2))
            topPosY += CInt((backImage.Height / 2) - (topImage.Height / 2))
 
            Dim bmp As New Bitmap(backImage.Width, backImage.Height)
 
            Using canvas As Graphics = Graphics.FromImage(bmp)
 
                canvas.InterpolationMode = Drawing2D.InterpolationMode.HighQualityBicubic
 
                canvas.DrawImage(image:=backImage,
                                 destRect:=New Rectangle(0, 0, bmp.Width, bmp.Height),
                                 srcRect:=New Rectangle(0, 0, bmp.Width, bmp.Height),
                                 srcUnit:=GraphicsUnit.Pixel)
 
                canvas.DrawImage(image:=topImage,
                                 destRect:=New Rectangle(topPosX, topPosY, topImage.Width, topImage.Height),
                                 srcRect:=New Rectangle(0, 0, topImage.Width, topImage.Height),
                                 srcUnit:=GraphicsUnit.Pixel)
 
                canvas.Save()
 
            End Using
 
            Return bmp
 
        End If
 
    End Function

/// <remarks>
/// *****************************************************************
/// Snippet Title: Overlay Images
/// Code's author: Elektro
/// Date Modified: 30-April-2015
/// *****************************************************************
/// </remarks>
/// <summary>
/// Overlay an image over a background image.
/// </summary>
/// <param name="backImage">The background image.</param>
/// <param name="topImage">The topmost image.</param>
/// <param name="topPosX">An optional adjustment of the top image's "X" position.</param>
/// <param name="topPosY">An optional adjustment of the top image's "Y" position.</param>
/// <returns>The overlayed image.</returns>
/// <exception cref="ArgumentNullException">backImage or topImage</exception>
/// <exception cref="ArgumentException">Image bounds are greater than background image.;topImage</exception>
public static Image OverlayImages(Image backImage, Image topImage, int topPosX = 0, int topPosY = 0)
{
 
        if (backImage == null) {
		throw new ArgumentNullException(paramName: "backImage");
 
	} else if (topImage == null) {
		throw new ArgumentNullException(paramName: "topImage");
 
	} else if ((topImage.Width > backImage.Width) || (topImage.Height > backImage.Height)) {
		throw new ArgumentException("Image bounds are greater than background image.", "topImage");
 
	} else {
		topPosX += Convert.ToInt32((backImage.Width / 2) - (topImage.Width / 2));
		topPosY += Convert.ToInt32((backImage.Height / 2) - (topImage.Height / 2));
 
		Bitmap bmp = new Bitmap(backImage.Width, backImage.Height);
 
		using (Graphics canvas = Graphics.FromImage(bmp)) {
			canvas.InterpolationMode = Drawing2D.InterpolationMode.HighQualityBicubic;
			canvas.DrawImage(image: backImage, destRect: new Rectangle(0, 0, bmp.Width, bmp.Height), srcRect: new Rectangle(0, 0, bmp.Width, bmp.Height), srcUnit: GraphicsUnit.Pixel);
			canvas.DrawImage(image: topImage, destRect: new Rectangle(topPosX, topPosY, topImage.Width, topImage.Height), srcRect: new Rectangle(0, 0, topImage.Width, topImage.Height), srcUnit: GraphicsUnit.Pixel);
 
			canvas.Save();
		}
		return bmp;
	}
}
 
//=======================================================
//Service provided by Telerik (www.telerik.com)
//=======================================================

Dim backImg As Image = Image.FromFile("C:\back.jpg")
Dim topImg As Image = Image.FromFile("C:\top.png")
Dim overlay As Image = OverlayImages(backImg, topImg, topPosX:=+5, topPosY:=-15)
overlay.Save("C:\Overlay.jpg", Imaging.ImageFormat.Jpeg)
Process.Start("C:\Overlay.jpg")

if (ComboBox.SelectedIndex != 1) {
    // ...
}

ComboBox1.SelectedItem = Nothing;

ComboBox1.SelectedIndex = -1;

...
ds.Clear();
dataAdap.Fill(ds);
...

    Private filterList As New List(Of String)
 
    Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs) _
    Handles MyBase.Load
 
        ' Set property names as tags
        Me.ComboBox1.Tag = "iddpto"
        Me.ComboBox2.Tag = "idprofe"
        Me.ComboBox3.Tag = "idmate"
        Me.ComboBox4.Tag = "idperi"
        Me.ComboBox5.Tag = "idtiposem"
 
    End Sub
 
    Private Sub ComboBox_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs) _
    Handles ComboBox1.SelectedIndexChanged,
            ComboBox2.SelectedIndexChanged,
            ComboBox3.SelectedIndexChanged,
            ComboBox4.SelectedIndexChanged,
            ComboBox5.SelectedIndexChanged
 
        Dim cb As ComboBox = DirectCast(sender, ComboBox)
 
        Me.filterList.Remove(Me.filterList.Find(Function(item As String) item Like String.Format("AND A.{0}*", cb.Tag.ToString)))
 
        If cb.SelectedIndex <> -1 Then
            Me.filterList.Add(String.Format("AND A.{0}='{1}'", cb.Tag.ToString, cb.SelectedItem.ToString))
        End If
 
#If DEBUG Then
        Debug.WriteLine(String.Join(" ", Me.filterList))
#End If
 
    End Sub

private List<string> filterList = new List<string>();
 
private void Form1_Load(object sender, EventArgs e) {
 
	// Set property names as tags
	this.ComboBox1.Tag = "iddpto";
	this.ComboBox2.Tag = "idprofe";
	this.ComboBox3.Tag = "idmate";
	this.ComboBox4.Tag = "idperi";
	this.ComboBox5.Tag = "idtiposem";
}
 
// nota: Este event-handler lo usas para suscribirte al evento 'SelectedIndexChanged' de TODOS los ComboBoxes.
private void ComboBox_SelectedIndexChanged(object sender, EventArgs e) {
 
	ComboBox cb = (ComboBox)sender;
        this.filterList.Remove(this.filterList.Find((string item) => item.StartsWith(string.Format("AND A.{0}", cb.Tag.ToString))))
 
	if (cb.SelectedIndex != -1) {
		this.filterList.Add(string.Format("AND A.{0}='{1}'", cb.Tag.ToString, cb.SelectedItem.ToString));
	}
 
	// #if DEBUG
	     Debug.WriteLine(string.Join(" ", this.filterList));
	// #endif
}