CODEWITHSUNDEEP
wpfxamlbinding
Vegar
Vegar

Reputation: 12898

DataTrigger, Binding to nested properties via TemplatedParent

According to msdn, it should be perfectly legal, and possible, to bind something to a nested property:

<Binding Path="propertyName.propertyName2" .../>
<Binding Path="propertyName.propertyName2.propertyName3" .../>

In my case, it's not so, though...

I have a custom control, MyControl, with a dependency property ViewModel:

    public static DependencyProperty ViewModelProperty = DependencyProperty.Register(
        "ViewModel", typeof(IViewModel), typeof(MyControl));

    public IViewModel ViewModel
    {
        get { return (IViewModel)GetValue(ViewModelProperty); }
        set { SetValue(ViewModelProperty, value); }
    }

and in the control template, I try to bind to properties in that viewmodel:

 <Style TargetType="{x:Type my:MyControl}">
   <Setter Property="Template">
     <Setter.Value>
       <ControlTemplate TargetType="{x:Type my:MyControl}">
         <Grid>
           <TextBox Text="{Binding RelativeSource={RelativeSource Mode=TemplatedParent}, Path=ViewModel.Text}"/>
           <Button x:Name="MyButton" Content="Visible by trigger" Visibility="Collapsed" />
         </Grid>
       <ControlTemplate.Triggers>
         <DataTrigger Binding="{Binding RelativeSource={RelativeSource Mode=TemplatedParent}, Path=ViewModel.ButtonVisible}" Value="True">
           <Setter TargetName="MyButton" Property="Visibility" Value="Visible" />
         </DataTrigger>            
      .../>

In the viewmodel itself, I have a preoperty Text as follow:

    public string Text
    {
        get { return m_text; }
        set
        {
            m_text = value;
            OnPropertyChanged("Text");
        }
    }

    public bool ButtonVisible
    {
      get { return m_buttonVisible; }
      set 
     { 
       m_buttonVisible = value; 
       OnPropertyChanged("ButtonVisible"); }
     }

I get no bind errors, but things doesn't happend...

Any clues?

Edit It looks like the bindings work half way. When the text is changed in the editbox, my Text property is set, but if the Text-property is set in code, the ui won't update.

Edit 2
Looks like my first attempt at simplifying the case before posting was a little to successful... As @Erno points out, the code that I posted seems to work OK.

I have looked at the original code some more, and added a trigger to the scenario. The original code uses triggers to show parts of the ui at given conditions. These are also binded to nested properties. I now think that these triggers fail to trigger. I have updated the code. If it still doesn't show whats wrong, I can post a sample application some where.

Upvotes: 1

Views: 4608

Answers (1)

Emond
Emond

Reputation: 50672

There is a comma missing:

<TextBox Text="{Binding RelativeSource={RelativeSource Mode=TemplatedParent}, Path=ViewModel.Text}"/>

EDIT

Add Mode=TwoWay to the binding:

<TextBox Text="{Binding RelativeSource={RelativeSource Mode=TemplatedParent}, Path=ViewModel.Text, Mode=TwoWay}"/>

EDIT2

Got it! I could reproduce and fix it.

Replace the TemplatedParent with Self in the binding. Read this explanation

Upvotes: 4

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