Thread: Using controls on Child from MdiParent

Hi,

I have an MDI windows form setup. On load it sets the child form(frmMainData) and opens it.

I have a progress bar on my child form that I wish to show(set to visible = false in design)

I have menu strip on my parent form.

For simplicity I have just set the command against one of the menustrip options to do the following

Code:

frmMainData.ProgressBar1.Show()

It does not work, there is no error the progressbar simply does not display.

That is my problem in a nutshell.

To add to this a little I actually have a sub in my child form that runs some code that I wish to execute from the menustrip and the code works fine, inside the code is some code to show the progress bar and it doesnt activate the progress bar, hence why I simplified the example above.

Thanks

Antony

Are you referring to default form instance, that 'frmMainData' is the class name, and is that also the mdi child form instance?

Yes the class name is frmMainData and I initiate the child form as frmMainData.

I can call a function on the child form from the parent menustrip fine and it will run the code in it.. apart from the references to the progress bar parts.. which is what prompted me to simple making the click event of the menu strip option to set the visible parameter to true of the progress bar to ensure nothing else was secretly causing it not to work!

Public Sub DatatableToExcel2()

        Dim _excel As Object

        Dim wBook As Object

        Dim wSheet As Object

        Dim res As DialogResult

        Dim filename As String

        filename = ""



        [B]Me.ProgressBar1.Show()

        Me.ProgressBar1.Maximum = _tmpDatatable.Rows.Count

        Me.ProgressBar1.Step = 1[/B]



        SaveFileDialog1.Filter = "(*.xls)|*.xls"

        SaveFileDialog1.Title = "Save Stock Proection Report Excel"

        res = SaveFileDialog1.ShowDialog()



        If res = DialogResult.OK Then

            If SaveFileDialog1.FileName <> "" Then

                filename = SaveFileDialog1.FileName

                'MsgBox(filename)

            End If



            _excel = CreateObject("Excel.Application")



            wBook = _excel.Workbooks.Add()

            wSheet = wBook.ActiveSheet()



            Dim dc As System.Data.DataColumn

            Dim dr As System.Data.DataRow

            Dim colIndex As Integer = 0

            Dim rowIndex As Integer = 0

            If _tmpDatatable IsNot Nothing Or _tmpDatatable.Rows.Count <> 0 Then





                For Each dc In _tmpDatatable.Columns

                    colIndex = colIndex + 1

                    _excel.Cells(1, colIndex) = dc.ColumnName

                Next



                For Each dr In _tmpDatatable.Rows

                    rowIndex = rowIndex + 1

                    colIndex = 0

                    For Each dc In _tmpDatatable.Columns

                        colIndex = colIndex + 1

                        If dc.ColumnName <> "Check" Then

                            If dc.ColumnName = "Item" Then

                                _excel.Cells(rowIndex + 1, colIndex) = "'" + dr(dc.ColumnName)

                            Else

                                _excel.Cells(rowIndex + 1, colIndex) = dr(dc.ColumnName)

                            End If

                        End If



                    Next

                    [B]Me.ProgressBar1.PerformStep()[/B]

                Next



                wSheet.Columns.AutoFit()



                Dim strFileName As String = filename

                If System.IO.File.Exists(strFileName) Then

                    System.IO.File.Delete(strFileName)

                End If



                wBook.SaveAs(strFileName)

                wBook.Close()

                _excel.Quit()

                [B]Me.ProgressBar1.Value = 0

                Me.ProgressBar1.Hide()[/B]

            Else

                MsgBox("nothing in datatable")

            End If

        End If

    End Sub

While your code is running in UI thread nothing else can happen in that thread. A cheap option, if your operation just takes a very few seconds to complete, is to call DoEvents to let all windows messages/events to be processed. The better option in most cases is to do any time consuming processing in a secondary thread, and invoke updates back to UI thread when necessary. The BackgroundWorker component is a simple way to add multithreading in a forms application, and it includes features such as progress/completion event notification back to UI thread.