Question

I recently upgraded a VB 6 project to .net. I’m having a problem with this block of code:

    Dim CtrlName As System.Windows.Forms.MenuItem

    For Each CtrlName In Form1.Controls

    'Some code here

    Next CtrlName

Now this code compiles but throws the following runtime error:

Unable to cast object of type ‘System.Windows.Forms.Panel’ to type ‘System.Windows.Forms.MenuItem.

I have a panel control on the subject form. How do I resolve this?
Thanks.

Answer 1

You are iterating over all controls that are directly inside the form, not just the MenuItems. However, your variable is of type MenuItem. This is causing the problem.

For normal controls (e.g. Buttons), you’d want to use the following, easy fix; test inside the loop whether the control type is correct:

For Each control As Control In Form1.Controls
    Dim btt As Button = TryCast(control, Button)
    If btt IsNot Nothing Then
        ' Perform action
    End If
Next

However, this does not work for MenuItems since these aren’t controls at all in WinForms, and they aren’t stored in the form’s Controls collection.

You need to iterate over the form’s Menu.MenuItems property instead.