Ask Kathleen

Visual Studio Debug Tips (Part 3): Disabled DataForm

Kathleen Dollard closes up her guidance on debugging code in Visual Studio with some troubleshooting of a disabled DataForm.

In the first part of Kathleen Dollard's column on tips and strategies for improving debugging in Visual Studio 2008 and 2010, she discussed useful strategies and explored the debug talents of the latest version of Visual Studio. In part 2, she explored how to use the built-in tracing capabilities of .NET to resolve pesky no-repro bugs. In the final installment, she helps a developer solve a problem with a misbehaving DataForm.

Q: I have a DataForm on a user control on a tab in a user control. After I display a child window, the DataForm appears disabled. What do you think is going on?

A: There are a couple of reasons this can happen. If you set the DialogResult and also call Close (generally setting the result inside the ChildWindow and calling Close from outside), the ChildWindow gets confused and leaves the underlying visuals disabled.

It sounds like you've encountered a different problem when the DataForm doesn't correctly re-enable itself. This is a bug that you can work around by altering the DataForm or issuing an explicit BeginEdit after the ChildWindow closes. The second approach works if the user expects to be editing the otherwise grayed-out fields.

I found the more involved fix of changing the DataForm on Stefan Olson's blog. The basic problem is that the DataForm doesn't correctly reset its visual state. Derive a new class from the DataForm, add a handler for IsEnabledChanged and explicitly set the visual state:

void wi_IsEnabledChanged(object sender, 
DependencyPropertyChangedEventArgs e)
{
if (!IsEnabled)
{ VisualStateManager.GoToState(this, "Disabled", true); }
else
{ VisualStateManager.GoToState(this, "Normal", true); }
}

This fix isn't free. Deriving a new class changes the control you're using. Theming works on the specific control, not its base classes -- therefore the implicit styling associated with themes won't work unless you update the theme.

About the Author

Kathleen is a consultant, author, trainer and speaker. She’s been a Microsoft MVP for 10 years and is an active member of the INETA Speaker’s Bureau where she receives high marks for her talks. She wrote "Code Generation in Microsoft .NET" (Apress) and often speaks at industry conferences and local user groups around the U.S. Kathleen is the founder and principal of GenDotNet and continues to research code generation and metadata as well as leveraging new technologies springing forth in .NET 3.5. Her passion is helping programmers be smarter in how they develop and consume the range of new technologies, but at the end of the day, she’s a coder writing applications just like you. Reach her at kathleen@mvps.org.

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