I've noticed that this occurs when I display the Window that is hosting the designer twice in the same process. The first time I display the Window it works as expected. The second time, the view has the strange behavior of showing duplicates. This makes me believe some static data is being updated in each instance of the view. The only static data updated in my code is within RegisterMetadata():

MetadataStore.AddAttributeTable(builder.CreateTable());

I made RegisterMetadata static and called it from my Window class's static initializer to ensure it was only called once. This didn't seem to have any effect, so I believe the WorkflowDesigner itself may have some static data that it is updating incorrectly.

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Hi Pastorius,

I couldn't understand from your bug report how you are showing and hiding the Window. If I create a window that just has a designer view, and shows and hides in response to button click from another window, I don't see any doubling effect.

Are you adding handlers for events, or doing some initialization steps more than once? If you have additional information to add, I'd appreciate it.

Thanks,
Tim

Tim,

Try this: change the HelloDesigner.MainWindow from the lab to a UserControl (adjusting the XAML and code behind file). Then add another Window to the project, make is the StartupURI in App.xaml, and give it the following markup, which hosts two instances of the designer Window on two TabItems in a TabControl. Run the project. Everything you add on the first tab will probably show up as normal. Everything you add on the second tab gets duplicated. I can zip up the project and send to you if needed.

<Window x:Class="HelloDesigner.Window1"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:HelloDesigner"
        Title="Window1" Height="300" Width="300">
    <Grid>
        <TabControl>
            <TabItem Header="Workflow1">
                <local:MainWindow />
            </TabItem>
            <TabItem Header="Workflow2">
                <local:MainWindow />
            </TabItem>
        </TabControl>
    </Grid>
</Window>

I went ahead and zipped and attached my slightly modified HelloDesigner project. Replace the HostedDesigner project under the VS2010 Training Kit with this project to see the problem. Here is the path to the whole solution from wherever you've unzipped the VS2010 Training Kit.

VS2010TrainingKit\Labs\IntroToWF\Source\Ex10-HostedDesigner\End\C#

Pastorius,
Thank you for the added repro information, I was able to reproduce the bug and have passed it on for triage.
Tim