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You can subclass ComboBox. In your derived class, make sure you set

  this.DrawMode = System.Windows.Forms.DrawMode.OwnerDrawFixed;
  this.DropDownStyle = ComboBoxStyle.DropDownList;

You also need to handle the DrawItem event to actually implement the drawing. Check out the details in the OwnerDrawnComboBox sample.

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This entry was created using the feedback provided by Jay Harlow in the newsgroups.

The enum values can be bound to a combobox as follows:


[C#]
// Setup the binding as follows:
// MyValues is the enum type
comboBox1.DataSource = Enum.GetValues(typeof MyValues);
[VB]
comboBox1.DataSource = Enum.GetValues(Type.GetType(MyValues))

Then in the SelectedValueChanged event for the ComboBox.


[C#]
private void ComboBox1ValueChanged(object sender, EventArgs e)
{
    MyValues v = (MyValues)this.comboBox1.SelectedValue;
}
[VB]
Private  Sub ComboBox1ValueChanged(ByVal sender As Object, ByVal e As EventArgs)
    Dim v As MyValues = CType(Me.comboBox1.SelectedValue, MyValues)
End Sub
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Here are some snippets. (Courtesy of Michael Lang)

[C#]
	DataTable list = new DataTable();
	list.Columns.Add(new DataColumn('Display', typeof(string)));
	list.Columns.Add(new DataColumn('Id', typeof(int)));
	list.Rows.Add(list.NewRow());
	list.Rows.Add(list.NewRow());
	list.Rows.Add(list.NewRow());
	list.Rows[0][0] = 'one';
	list.Rows[0][1] = 1;
	list.Rows[1][0] = 'two';
	list.Rows[1][1] = 2;
	list.Rows[2][0] = 'three';
	list.Rows[2][1] = 3;
	comboBox1.DataSource = list;
	comboBox1.DisplayMember = 'Display';
	comboBox1.ValueMember = 'Id';

[VB.NET]
	Dim list As New DataTable()
	list.Columns.Add(New DataColumn('Display', GetType(String)))
	list.Columns.Add(New DataColumn('Id', GetType(Integer)))
	list.Rows.Add(list.NewRow())
	list.Rows.Add(list.NewRow())
	list.Rows.Add(list.NewRow())
	list.Rows(0)(0) = 'one' ’
	list.Rows(0)(1) = 1 ’
	list.Rows(1)(0) = 'two' ’
	list.Rows(1)(1) = 2 ’
	list.Rows(2)(0) = 'three' ’
	list.Rows(2)(1) = 3 ’
	comboBox1.DataSource = list
	comboBox1.DisplayMember = 'Display'
	comboBox1.ValueMember = 'Id'
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You can avoid the combobox dropping by overriding its WndProc method and ignoring the WM_LBUTTONDOWN and WM_LBUTTONDBLCLK.

[C#]
 public class MyComboBox : ComboBox
 {
	protected override void WndProc(ref System.Windows.Forms.Message m)
	{
		 if(m.Msg == 0x201  //WM_LBUTTONDOWN
		    || m.Msg == 0x203)  //WM_LBUTTONDBLCLK
  			 return;
		base.WndProc(ref m);
	}
 }

[VB.NET]
Public Class MyComboBox
	Inherits ComboBox
   
	Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
		If m.Msg = &H201 OrElse m.Msg = &H203 Then ’WM_LBUTTONDOWN  or WM_LBUTTONDBLCLK
			Return
		End If

		MyBase.WndProc(m)
	End Sub ’WndProc
End Class ’MyComboBox
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You can iterate through the list to find the longest text extent using MeasureString, and then use this as the combobox width adding a fudge factor for the dropdown button.

	System.Drawing.Graphics g = comboBox1.CreateGraphics();
	float maxWidth = 0f;
	foreach(object o in comboBox1.Items)
	{
		float w = g.MeasureString(o.ToString(), comboBox1.Font).Width;
		if(w > maxWidth)
			maxWidth = w;
	}
	g.Dispose();
	comboBox1.Width = (int) maxWidth + 20; // 20 is to take care of button width
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