Question

The following Microsoft example code contains the following:

<Grid>
...     
  <Border Name="Content" ... >
...     
  </Border>
</Grid>
<ControlTemplate.Triggers>
  <Trigger Property="IsExpanded" Value="True">
     <Setter TargetName="ContentRow" Property="Height"
             Value="{Binding ElementName=Content,Path=DesiredHeight}" />
  </Trigger>
...
</ControlTemplate.Triggers>

When run, however, this code generates the following databinding error:

System.Windows.Data Error: 39 : BindingExpression path error: 'DesiredHeight' property not found on 'object' ''Border' (Name='Content')'. BindingExpression:Path=DesiredHeight; DataItem='Border' (Name='Content'); target element is 'RowDefinition' (HashCode=2034711); target property is 'Height' (type 'GridLength')

Despite this error, the code works correctly. I have looked through the documentation and DesiredHeight does not appear to be a member of Border. Can anyone explain where DesiredHeight is coming from? Also, is there any way to resolve/suppress this error so my program output is clean?

Answer 1

You can see that property in the code part of your application

Edit:

Border content = new Border();
int desiredHeight = content.DesiredSize.Height;
int desiredWidth = content.DesiredSize.Width;

To solve the problem try binding it to the Height attribute, since DesiredHeight doesn’t seem to be available in the XAML markup of the Border control.