ErikE ErikE - 11 days ago 5
C# Question

.Net TableLayoutPanel – Clearing Controls is Very Slow

This is really simple.

I have a TableLayoutPanel that is populated with controls (just Labels, Buttons, and some Panels with buttons) based on a database query. When the data needs to be refreshed, I use TableLayoutPanel.Controls.Clear(). Unfortunately, this is a very slow operation. I would expect it to be faster than the code populating the table, but it is at least 3 or 4 times slower.

I definitively proved that the slowness is when executing Controls.Clear() by executing this as the single thing done to the TableLayoutPanel after a message box is displayed (then the procedure returns). The controls visibly disappear from the bottom up. When the recordset is used to repopulate the TableLayoutPanel, the speed of the controls appearing from top to bottom is almost faster than I can see.

I'm already doing TableLayoutPanel.SuspendLayout() and ResumeLayout().

Using

this.DoubleBuffered = true
on the form doesn't appear to do anything.

I could just Dispose the entire control and recreate it through code, but this is a big pain and makes having a nice form designer GUI pointless. I would have to dig into every property I've set on the control and create a line of code for it (though I guess I could get this out of the designer code itself, it still feels wrong).

Any ideas on how to do the job faster? I'm even open to using other methods besides a TableLayoutPanel... I just need the freedom to put multiple buttons per cell or barring that to be able to span columns in the table header.

Can C# at least freeze the whole form while it redraws and then paint all at once?

Answer

I've run into issues with slowness using TableLayoutPanels as well. Rather than setting the DoubleBuffered property on the form, the best solution I have found is to create a new class that inherits from TableLayoutPanel, and in that class' constructor, enable double-buffering:

public class DoubleBufferedTableLayoutPanel : TableLayoutPanel
{
    public DoubleBufferedTableLayoutPanel()
    {
        DoubleBuffered = true;
    }
}

Then, use the DoubleBufferedTableLayoutPanel wherever you would normally use a TableLayoutPanel.

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