ContentControl does not change the content - function never called

问题

I want to change my content off an AppBar dynamicly whith this code:

<Page.Resources>
    <local:AppBarSelector x:Key="myAppBarSelector"/>
</Page.Resources>

<Page.BottomAppBar>
    <AppBar>
        <ContentControl Content="{Binding SelectedItem, ElementName=listBox}" ContentTemplateSelector="{StaticResource myAppBarSelector}">
            <ContentControl.Resources>
                <DataTemplate x:Key="1">
                    <TextBlock Text="Hallo Welt 1" Foreground="White" />
                </DataTemplate>

                <DataTemplate x:Key="2">
                    <TextBlock Text="Hallo Welt 2" Foreground="White" />
                </DataTemplate>
            </ContentControl.Resources>
        </ContentControl>
    </AppBar>
</Page.BottomAppBar>

And this is my Code behind:

public class AppBarSelector : DataTemplateSelector
{
    protected override DataTemplate SelectTemplateCore(object item, DependencyObject container)
    {
        Debug.WriteLine((string)item);
        if (item == null) return base.SelectTemplateCore(item, container);

        var contentControl = (ContentControl)container;
        var templateKey = (string)item;

        return (DataTemplate)contentControl.Resources[templateKey];
    }
}

But this method is nerver called.Even the Debug.WriteLine function. Where is my mistake?

回答1:

Just after some comments here...
(note: this is a bit general but I can't be more specific w/o some more code to reflect the issues)

This should work 'as is' - I don't see any problems that would produce that (I check with similar example fast and it works well with .ItemsSource = new List<string>{...}.

So that's not the culprit - but it doesn't hurt what I suggested - make a proper MVVM binding to properties, make the list ObservableCollection<> - and also it's always recommended to have a more higher-level objects (instead of just string) as your items (helps in many cases with binding with similar issues - that object implements INotifyPropertyChanged etc. - and you bind to a 'property' there, not the entire object).

The other error suggests some issues as well.

And lastly to bind two contentControls together - you don't normally need events as such. You can use Triggers from the style or XAML directly - but most of the time just bind both to a property in the view-model - and handle the 'change' in your property 'setter'.

You should put up a small primer that repeats this - who knows it might help you realize what you're doing wrong.

来源：https://stackoverflow.com/questions/16252349/contentcontrol-does-not-change-the-content-function-never-called

标签

xaml

windows-8

contentcontrol

datatemplateselector