Invalid Cast Errors

[Alan]

I keep getting an invalid cast error on this line of code:

Dim gridCol As MyGridColumn = CType(dgt.GridC olumnStyles(hi. Column),
MyGridColumn)

I am trying to develop a sub that will change the colors on a cell that
is clicked on in a DataGrid control.

Here is the full code:

Private Sub PaintCell(ByVal sender As Object, ByVal e As
MouseEventArgs)

Try
Dim hi As DataGrid.HitTes tInfo
Dim grid As DataGrid = CType(sender, DataGrid)
hi = grid.HitTest(e. X, e.Y)
If hi.Type = DataGrid.HitTes tType.Cell Then
Dim dgt As DataGridTableSt yle =
dgvBranches.Tab leStyles(0)
Dim cm As CurrencyManager =
CType(Me.Bindin gContext(myData Set.Tables(0)), CurrencyManager )
Dim cellRect As Rectangle
cellRect = grid.GetCellBou nds(hi.Row, hi.Column)
Dim gridCol As MyGridColumn =
CType(dgt.GridC olumnStyles(hi. Column), MyGridColumn)
Dim g As Graphics = dgvBranches.Cre ateGraphics()
Dim fBrush As New SolidBrush(Colo r.Blue)
Dim bBrush As New SolidBrush(Colo r.Yellow)
gridCol.PaintCo l(g, cellRect, cm, hi.Row, bBrush,
fBrush, False)
End If
Catch ex As Exception
LogErrors(ex, "PaintCell" )
End Try
End Sub 'PaintCell


Any help would be appreciated. Thanks!

[Chris Dunaway]

Re: Invalid Cast Errors

What data type is MyGridColumn? Does it inherit from another class?
Is the class it inherits from a DataGridColumnS tyle? The
dgt.GridColumnS tyles collection is a collection of DataGridColumnS tyle
so if your gridCol is not a DataGridColumnS tyle or a class that
inherits from it, the cast wont work.

Also, I noticed that your sub create a number of objects that need to
be disposed, namely the Graphics object and the Brush objects. You
should call .Dispose on these objects to free up their unmanaged
resources.

[Alan]

Re: Invalid Cast Errors

Sorry I knew there was something I forgot to add to this:

Public Class MyGridColumn
Inherits DataGridTextBox Column
Public Sub PaintCol(ByVal g As Graphics, ByVal cellRect As
Rectangle, _
ByVal cm As CurrencyManager , ByVal rowNum As Integer, ByVal bBrush
As Brush, _
ByVal fBrush As Brush, ByVal isVisible As Boolean)
Me.Paint(g, cellRect, cm, rowNum, bBrush, fBrush, isVisible)
End Sub
End Class

Perhaps that will answer your questions Chris.

[Alan]

Re: Invalid Cast Errors

Needless to say I still get the error.

[Chris Dunaway]

Re: Invalid Cast Errors

Are the items in dgt.GridColumnS tyles in fact instances of
MyGridColumn? Can you verify using the debugger what type
dgt.GridColumnS tyles(hi.Column ) is? If it is a MyGridColumn instance
then I don't know why the cast is not working.

If if is an instance of one of the base classes (DataGridTextBo xColumn
or DataGridColumnS tyle) then the cast won't work because you can't cast
from a base type to a derived type unless the object is, in fact, an
instance of the derived type.

PS. I still stand by recommendation to Dispose your brushes and
Graphics instances.