DataTrigger is not working in xaml wpf

Question

Hi All,
I want to change the Data templates dynamically based on some selection. Here I have used DataTrigger to which I have binded a property which is not working. I don't know why its not working.
Please find below .xaml code -                                
        <DataTemplate x:Key="StackTemplate">
            <TextBlock x:Name="txtStack" Text="We are using Stack Panel"></TextBlock>
        </DataTemplate>
        <DataTemplate x:Key="DockTemplate">
            <TextBlock x:Name="txtDock" Text="We are using Dock Panel"></TextBlock>
        </DataTemplate>
        <DataTemplate x:Key="WrapTemplate">
            <TextBlock x:Name="txtWrap" Text="We are using Wrap Panel"></TextBlock>
        </DataTemplate>
        <DataTemplate x:Key="CanvasTemplate">
            <TextBlock x:Name="txtcanvas" Text="we are using Canvas panel"></TextBlock>
        </DataTemplate>
    </Window.Resources>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="50"></RowDefinition>
            <RowDefinition Height="*"></RowDefinition>
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="170"></ColumnDefinition>
            <ColumnDefinition Width="*"></ColumnDefinition>
        </Grid.ColumnDefinitions>
        <TextBlock Grid.Column="0" Grid.Row="0" x:Name="Txtblk" Text="Choose Layout Panel"></TextBlock>
        <ComboBox Grid.Column="1" Width="200"  ItemsSource="{Binding Source={StaticResource LoadCombo}}" Margin="66,12,66,0"></ComboBox> // loaded from xaml
        <ItemsControl Grid.Column="1" Grid.Row="1" x:Name="itemctrl" Height="250" Width="280">
            <DataTemplate>
                <ContentControl Content="{Binding}">
                    <ContentControl.Style>
                        <Style TargetType="{x:Type ContentControl}">
                            <Style.Triggers>
                                <DataTrigger Binding="{Binding Path=MyProperty,RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}" Value="0">
                                    <Setter Property="ContentTemplate" Value="{StaticResource StackTemplate}"></Setter>
                                </DataTrigger>
                                <DataTrigger Binding="{Binding Path=MyProperty,RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}" Value="1">
                                    <Setter Property="ContentTemplate" Value="{StaticResource DockTemplate}"></Setter>
                                </DataTrigger>
                                <DataTrigger Binding="{Binding Path=MyProperty,RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}" Value="2">
                                    <Setter Property="ContentTemplate" Value="{StaticResource WrapTemplate}"></Setter>
                                </DataTrigger>
                                <DataTrigger Binding="{Binding Path=MyProperty,RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}" Value="3">
                                    <Setter Property="ContentTemplate" Value="{StaticResource CanvasTemplate}"></Setter>
                                </DataTrigger>                                
                            </Style.Triggers>
                        </Style>
                    </ContentControl.Style>
                </ContentControl>
            </DataTemplate>
        </ItemsControl>
Here is my .xaml.cs class - 
  public partial class MainWindow : Window
        public string Select { get; set; }
        public string MyProperty
            get
                string number=string.Empty;
                switch (Select)
                    case "STACKPANEL": 
                        number = "0"; break;
                    case "DOCKPANEL":
                        number = "1"; break;
                    case "WRAPPANEL":
                        number = "2"; break;
                    case "CANVAS":
                        number= "3"; break;
                return number;
        public MainWindow()
            InitializeComponent();
            DataContext = this;
            Select = "0";
            cmb.SelectionChanged += new SelectionChangedEventHandler(cmb_SelectionChanged);
        void cmb_SelectionChanged(object sender, SelectionChangedEventArgs e)
            Select = (sender as ComboBox).Text;
Please help me.

Answer 1

That isn't going to work.
Selecting datatemplate is a one off process.
When you're looking at the view, it's done.
I think if you used a contenttemplateselector you could force the issue:
MyControl.ContentTemplateSelector =
new MyDataTemplateSelector();
I very rarely use those myself though.
Personally, I would be inclined to just switch out the control for a new one with the appropriate template.
It's a view responsibility so doing that in code behind isn't even breaking mvvm.
Your code coverage might dip a little, but this doesn't look like a real app anyhow.
I agree with Andy, using DataTemplateSelector should be the right direction, please refer to this case to know how it works:
https://social.msdn.microsoft.com/Forums/vstudio/en-US/f7c60968-f3a0-499a-a20e-01aac82d942f/datatemplate-for-generic-type-is-not-working?forum=wpf
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