How to bind to a WPF dependency property when the datacontext of the page is used for other bindings?

Question

How to bind to a WPF dependency property when the datacontext of the page is used for other bindings? (Simple question)

Answer 1

The datacontext of the element needed to be set.

XAML:

<Window x:Class="WpfDependencyPropertyTest.Window1" x:Name="mywindow">
   <StackPanel>
      <Label Content="{Binding Path=Test, ElementName=mywindow}" />
   </StackPanel>
</Window>

C#:

public static readonly DependencyProperty TestProperty =
        DependencyProperty.Register("Test",
                                    typeof(string),
                                    typeof(Window1),
                                    new FrameworkPropertyMetadata("Test"));
public string Test
{
   get { return (string)this.GetValue(Window1.TestProperty); }
   set { this.SetValue(Window1.TestProperty, value); }
}

Also see this related question:

WPF DependencyProperties

Answer 2

In XAML:

Something="{Binding SomethingElse, ElementName=SomeElement}"

In code:

BindingOperations.SetBinding(obj, SomeClass.SomethingProperty, new Binding {
  Path = new PropertyPath(SomeElementType.SomethingElseProperty),  /* the UI property */
  Source = SomeElement /* the UI object */
});

Though usually you will do this the other way round and bind the UI property to the custom dependency property.