Binding to an element within a UserControl

Question

Say I have a user control like the one below, how would I bind something to the ActualWidth of the "G1" grid from outside of the control?

<UserControl x:Class="Blah">
  <WrapPanel>
    <Grid x:Name="G1">
      ...
    </Grid>
    <Grid>
      ...
    </Grid>
  </WrapPanel>
</UserControl>

What do you mean by 'out side of G1' - From the same XAML file or from Code behind? — Jobi Joy, Nov 21 '08 at 02:48

score 2 · Answer 1 · edited Jun 13 '13 at 19:20

2

If you mean with outside the control, not as Content of the control, you can use ElementName in the Binding like so:

{Binding ElementName=G1, Path=ActualWidth}

If you mean outside the control in another Xaml file, then you can try to use the Path property if your control is in the scope of the other control:

{Binding ElementName=ParentControl, Path=G1.ActualWidth}

However I would advise against this design, because you may change the name of G1 one day, and you would never know of any bindings that might break.

edited Jun 13 '13 at 19:20

Dave Clemmer

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answered Nov 21 '08 at 10:40

Arcturus

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{Binding ElementName=ParentControl, Path=G1.ActualWidth} doesn't work & the control is in scope - I can see the actual width of the whole control. – MJS Nov 24 '08 at 00:58

score 1 · Answer 2 · edited Jun 13 '13 at 16:40

1

If you want to bind to an external control where you use this user control, declare a DependencyProperty at your UserControl code behind and then Bind G1 to that property. And bind the external control's property to the UserControl's DependencyProperty. It is like a 2 level of indirection.

edited Jun 13 '13 at 16:40

Dave Clemmer

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answered Nov 21 '08 at 02:52

Jobi Joy

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but ActualWidth won't bind in this way? – MJS Nov 23 '08 at 21:24
a related question: http://stackoverflow.com/questions/313124/wpf-usercontrol-expose-actualwidth – MJS Nov 24 '08 at 00:52

Binding to an element within a UserControl

2 Answers2