form.showDialog()

I have three forms: A, B and C

There is a button on A to load B, and a button on B to load C, which has a datagrid with checkbox column.

I use showDialog() to load the forms.

When I click the checkbox on C's datagrid, i get error on A's button click event "An unhandled exception of type 'System.InvalidCastException' occurred in system.windows.forms.dll

Additional information: Specified cast is not valid."

Any idea? Thanks.

Yes! Vb.NET has a particular and misterious way to show its errors.
The error is probably in the code of Form C, as you can imagine, but when forms are showed as Modal (like ShowDialog), VB.NET make green the code line in which the form is showed. I don't know why, but I've verified this. You have to follow your application step by step and you will catch the mistake.
Good job!:)

Thanks for your reply.

Yes, i think the error is about Form C. in particularly, the bool column in that datagrid. The first time i click the checkbox, it is ok, but if i check again, :(

Here is the code for that boolean column:

VB Code:

Dim activeCol As DataGridBoolColumn = New DataGridBoolColumn()
        activeCol.MappingName = "Active"
        activeCol.HeaderText = "Active"
        activeCol.AllowNull = False
        activeCol.FalseValue = CShort(0)
        activeCol.ReadOnly = False
        activeCol.TrueValue = CShort(1)
        activeCol.Width = 100
        activeCol.Alignment = HorizontalAlignment.Center
        dgts.GridColumnStyles.Add(activeCol)

I must stop here, because I've never used a datagrid! Anyway the kind of error says to us that your application is trying to put a certain type of data in a place that is made for a different one, or something like this!
Good job:wave:

thank you, alextyx.