binding declared in xaml does not work

Question

I have a main window which contains a grid, during the window loaded event, I will dynamically create an instance of a user control and add it to grid. In order to let the user control to adapt itself when the main window is resized, I want to bind the user control's width and height to the grid's ActualWidth and ActualHeight.

The first way is to create the binding object in code,same place in the window_loaded event,

Binding widthBinding = new Binding("ActualWidth");
widthBinding.Source = panel;
BindingOperations.SetBinding(uc, WidthProperty, widthBinding);

Binding heightBinding = new Binding("ActualHeight");
heightBinding.Source = panel;
BindingOperations.SetBinding(uc, HeightProperty, heightBinding);

panel.Children.Add(uc);

it worked as expected.

The second way is to use xaml binding in the user control's xaml file,

<UserControl x:Class="S2T.RAHS2.ContentAcquisition.FileViewer.WordViewer"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Loaded="UserControl_Loaded" Unloaded="UserControl_Unloaded" 
    Width="{Binding ElementName=ContainerElement, Path=ActualWidth}"
    Height="{Binding ElementName=ContainerElement, Path=ActualHeight}">

or

 <UserControl x:Class="S2T.RAHS2.ContentAcquisition.FileViewer.WordViewer"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Loaded="UserControl_Loaded" Unloaded="UserControl_Unloaded" 
        Width="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type Grid}, AncestorLevel=1}, Path=ActualWidth}"
        Height="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type Grid}, AncestorLevel=1}, Path=ActualHeight}">

But this did not work.

May I know what is wrong with the xaml approach?

Can you post the output window binding errors for the two XAML scenarios you posted. Also can you post the XAML for the grid that you are adding this UserControl to. Is the grid the immediate parent of this UserControl? — Brad Cunningham, Dec 21 '09 at 06:15
I created a new test, and now everything works. If I use a grid as the parent of the user control, I do not need to insert any binding. If I use a stackpanel, the above two xmal bindings are effective. What I do not understand is why previous test did not work, since I changed a lot in the old test project, I could not retrieve back the previous code. — intangible02, Dec 28 '09 at 10:05

score 0 · Answer 1 · edited Jun 13 '13 at 16:54

Can you try using the alignments instead of binding?

<UserControl x:Class="S2T.RAHS2.ContentAcquisition.FileViewer.WordViewer"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Loaded="UserControl_Loaded" Unloaded="UserControl_Unloaded" 
        HorizontalAlignment="Stretch" VerticalAlignment="Stretch"/>

The problem with binding is that the ActualHeight and ActualWidth might increase if something in the panel makes it increase. This is especially true with StackPanels.

If you arr using a Grid, it might work with binding to the parent ActualWidth and ActualHeight. I have found that sometimes it works, but often something in the panel makes the size increase and messes up the binding.

Hi Andrew, both HorizonalAlignment and VerticalAlignment is set to stretch. — intangible02, Dec 11 '09 at 07:52

binding declared in xaml does not work

1 Answers1