I have an issue where a ComboBox control will change it's Text value when it is resized. Here is some sample code that I worked up:
Option Explicit On
Option Strict On
Public Class FMain
Private Sub FMain_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
uxComboBox.DropDownStyle = ComboBoxStyle.DropDown
uxComboBox.AutoCompleteSource = AutoCompleteSource.ListItems
uxComboBox.AutoCompleteMode = AutoCompleteMode.Suggest
ComboTest()
End Sub
Private Sub ComboTest()
Dim value As String = "6"
uxComboBox.Text = String.Empty
uxComboBox.Items.Clear()
uxComboBox.Items.AddRange(New String() {"4 9/16", "6 9/16", "7 9/16", "8 9/16"})
Dim index As Integer = uxComboBox.FindStringExact(value)
If uxComboBox.SelectedIndex index Then
uxComboBox.SelectedIndex = index
End If
If uxComboBox.SelectedIndex = -1 AndAlso _
Not String.Equals(uxComboBox.Text, value, StringComparison.OrdinalIgnoreCase) Then
uxComboBox.Text = value
End If
' unselect the text in the combobox
'
uxComboBox.Select(0, 0)
End Sub
End Class
Note that this form (FMain) has a single combobox on it (uxComboBox) that is docked to the top. When I run the code I see that the combobox has a value of "6" which is what I would expect. When I then resize the form, the combobox gets a value of "6 9/16" which is what I would NOT expect.
Does anyone know why this happens? Any suggested workarounds?
Thanks!
Stephen
Best Answer
Yes, this is a known bug in the native Windows implementation of ComboBox. There's another aspect to this bug. Put a button on your form and give it TabIndex = 0, change the CB's TabIndex to 1. Run it, the button will have the focus. Resize. Note that the ComboBox's text changes as before but now also gets highlighted, as though it has the focus. Even though it hasn't.
I think this bug has been around since Vista, it didn't get fixed in Win7. There's no known workaround for it.