If you're using WPF and doing any databinding, make sure you read KB article at Microsoft carefully:

A memory leak may occur when you use data binding in Windows Presentation Foundation

A snippet from the KB article:

This issue occurs if the following conditions are true:

• A data-binding path refers to property P of object X.
• Object X contains a direct reference or an indirect reference to the target of the data-binding operation.
• Property P is accessed through a PropertyDescriptor object instead of a DependencyProperty object or a PropertyInfo object.

In the following code example, the conditions for the leak are created.

<Label Name="MyLabel">
   <Stack Panel Name="MyStackPanel">
      <TextBlock Text="{Binding ElementName=MyStackPanel, 
Path=Children.Count}" />
   </StackPanel>
</Label>

Yes, it's really that simple! There are some work around methods, IF you happen to own the object you're binding to ... if not, you may need to create a facade/shim around the object.