RemoveRange and MessageBox in Update block cause hang

[Greg Wright]

I having some issues with displaying a message box within a BeginUpdate/EndUpdate block. Any of the following cause the app to hang once it reaches the MessageBox.Show line.

Ex. #1

this.gridControl1.BeginUpdate();
// If the RemoveRange is removed, it doesn''t hang
this.gridControl1.Rows.RemoveRange(2, 2);
MessageBox.Show("Testing.");
this.gridControl1.EndUpdate();

Ex. #2 - Same as Ex. #1, but in a try block w/ MessageBox in catch

try
{
Cursor.Current = Cursors.WaitCursor;
this.gridControl1.Model.BeginUpdate();

this.gridControl1[1, 1].Text = "1,1";

this.gridControl1.Rows.RemoveRange(2, 2);

throw new Exception("This is a test exception.");

}
catch (Exception e1)
{
MessageBox.Show(e1.Message);
}
finally
{
this.gridControl1.Model.EndUpdate();
this.gridControl1.Model.Refresh();
Cursor.Current = Cursors.Arrow;
}

Ex. #3 - Uses the Invalidate option on BeginUpdate. Differs from other examples in that RemoveRange doesn''t even have to be called. Will hang just by changing a cell value.

try
{
Cursor.Current = Cursors.WaitCursor;
this.gridControl1.BeginUpdate(BeginUpdateOptions.Invalidate);

this.gridControl1[1, 1].Text = "1,1";

throw new Exception("This is a test exception.");
}
catch (Exception e1)
{
MessageBox.Show(e1.Message);
}
finally
{
this.gridControl1.EndUpdate(true);
Cursor.Current = Cursors.Arrow;
}

Am I doing something wrong, or is this an issue. I am using version 2.0.5.1.

Thanks,

Greg

[Administrator]

You will not be able to display a messagebox while a grid.BeginUpdate is open.

You might try calling grid.CancelUpdate before you try to display the message.

Or, depending upon where this code is located (whether it is part of the current cell deactivate/activate cycle), you may be able to display an error message just by setting grid.CurrentCell.ErrorMessage. If this string is not empty, the grid will display it at a safe point in the deactivate/activate cycle.

Or, another option would be to set a flag in your code where you are now trying to display the messagebox, and then check that flag and display the messagebox after your call to EndUpdate if necessary.

[Greg Wright]

Clay,

Thanks for the quick response. If you wouldn''t mind, could you give me a little more detail as to why a messagebox can''t be displayed while a BeginUpdate is open so I can have a better understanding? I have done it without any problems, except for this one, where RemoveRange is called prior to displaying the messagebox.

Thanks,

Greg

[Administrator]

If the grid is in Update mode then WM_PAINT messages are not being handled in WndProc, and this causes a lockup in this case.

The grid tries to listen to WM_KILLFOCUS message and call CancelUpdate in WndProc to avoid this problem, but that only works in 50% of cases.

Explicitly calling CancelUpdate before you try displaying the MesageBox may work for you.

[Greg Wright]

Thanks Clay.

>If the grid is in Update mode then WM_PAINT messages are not being handled in WndProc, and this causes a lockup in this case.
>
>The grid tries to listen to WM_KILLFOCUS message and call CancelUpdate in WndProc to avoid this problem, but that only works in 50% of cases.
>
>Explicitly calling CancelUpdate before you try displaying the MesageBox may work for you.