How can I handle ComboBox selected index changing?

Question

I have a ComboBox that have a list of manufacturers. When a user selects a manufacturer, a grid below is populated with data for the chosen manufacturer. That data can be mo

Answer 1

I know this is an older question but I thought I'd add the method that I used. I'm not sure if it's any better. There should be a IndexChanging event or something in the regular ComboBox that can be cancelled.

The solution is a combination of @AftabAhmedKalhoro's and @jeffamaphone's posts but using the Tag property instead.

I didn't want to sub class the ComboBox, or have any extra private variables floating around in the form. But some might not like the Tag property, because it is kind of hidden if you're not use to using it (kind of left over from VB6).

Private Sub MainForm_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    ComboBox1.Items.Add("Item1")
    ComboBox1.Items.Add("Item2")
    ComboBox1.Items.Add("Item3")
    ComboBox1.Items.Add("Item4")
    ' Load Value from database or whatever and set the value or index.
    ComboBox1.SelectedIndex = 0
    ComboBox1.Tag = ComboBox1.SelectedIndex

    ' I add the handler at the end because I don't want it to fire during loading the form.
    AddHandler ComboBox1.SelectedIndexChanged, New EventHandler(AddressOf ComboBox1_SelectedIndexChanged)
End Sub

Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs)
    If (ComboBox1.Tag <> ComboBox1.SelectedIndex) Then
        If MessageBox.Show("Warning! You are changing the index." & vbCrLf & _
                           "Do you wish to continue?", _
                           "Changing Index", _
                           MessageBoxButtons.YesNo, _
                           MessageBoxIcon.Warning) = Windows.Forms.DialogResult.Yes Then
            ComboBox1.Tag = ComboBox1.SelectedIndex
            ' Do Something.
        Else
            ComboBox1.SelectedIndex = ComboBox1.Tag
        End If
    End If
End Sub

Note that resetting the SelectedIndex will cause the event to fire again in this line:

ComboBox1.SelectedIndex = ComboBox1.Tag