Diederik Krols

The XAML Brewer

Workaround: WPF DataGrid hangs Visual Studio.NET

Welcome to a WPF DataGrid crash course ... literally. It will show you how Cider can give you a hangover.  It took me 45 minutes, 10 process kills, and a full reboot to figure out what was going on in my application, so I gladly share my experience.

 Part one: the bug

Create a WPF Form with an empty DataGrid, like this:

<Window x:Class="U2UConsult.DockOfTheBay.DataGridWorkaround"

   xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

   xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

   xmlns:toolkit="http://schemas.microsoft.com/wpf/2008/toolkit"

   Title="Bug Workaround" SizeToContent="WidthAndHeight">

    <Grid>

        <toolkit:DataGrid>

            <toolkit:DataGrid.Columns>

            </toolkit:DataGrid.Columns>

        </toolkit:DataGrid> 

    </Grid>

</Window>

 

Then, add a style that adds a Margin to the Button control, e.g. as a Resource for the Window:

 <!-- Kaboom-->

<Window.Resources>

    <Style TargetType="{x:Type Button}">

        <Setter Property="Margin" Value="3" />

    </Style>

</Window.Resources>

 

Now is a good time to save your solution.

Add a column to the DataGrid:

<toolkit:DataGridTextColumn Header="Test" />

 

You will probably see something like this now, with an ever increasing counter:

Cider -the WPF Designer for Visual Studio.NET- entered an infinite loop.

Start Task Manager and inspect Visual Studio.NET's process, it's consuming close to 100% CPU:

Kill the process.

What you just experienced is a confirmed bug. The current version of the WPF DataGrid hangs Visual Studio.NET's Designer when buttons are decorated with a margin.

Part two: the Workaround

So now you know what may cause this behavior. Fortunately this shouldn't stop you from using a DataGrid, because the workaround is simple. All you need to do is embed a style in your DataGrid that resets the button margin to zero:

<toolkit:DataGrid>

    <!-- Workaround for bug: No button margins allowed -->

    <Style TargetType="{x:Type Button}">

        <Setter Property="Margin" Value="0" />

    </Style>

    <!-- End of Workaround -->

    <toolkit:DataGrid.Columns>

        <toolkit:DataGridTextColumn Header="Test" />

    </toolkit:DataGrid.Columns>

</toolkit:DataGrid>

 

This is just one of the many inconveniences with the current version of the toolkit. I strongly advise you to regularly check the issue tracker if you're planning to use its components in production.

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