Own DataTemplateSelector MVVM - mvvm

Question

I'm using a MVVM-Pattern with a ModelView-First approach. This works fine, so far.
Now I have a UserControl (View) which should display various content depending on a Property located in my ViewModel.
First, I tried to solve the issue with DataTemplates and a DataTemplateSelector (See this tutorial) This was working very well. But I was not happy with the solution, because then I have a class (the overrided DataTemplateSelector) which is not connected to the ViewModel and can't be filled from the model.
So I tried to create a own TemplateSelector which uses a Property from the ViewModel. Unfortunately the DataTrigger is not triggering. The Binding from a CheckBox to the ViewModel is also working but not at the DataTrigger (even the designer can't find this path).
Ok, please have a look at the code:
<UserControl.Resources>
<!--Define Template which is displayed for Users-->
<DataTemplate x:Key="templateUser">
<Image
Name="logo"
Source="blanked out"
HorizontalAlignment="Center"
VerticalAlignment="Center" />
</DataTemplate>
<!--Define Template which is displayed for Administrators-->
<DataTemplate x:Key="templateAdmin">
<TextBlock Background="Yellow" Margin="3" Text="YEAH, I'm an Administrator" />
</DataTemplate>
<!--My own TemplateSelectpr-->
<DataTemplate x:Key="myTemplateSelector">
<ContentControl x:Name="DynamicContent" ContentTemplate="{StaticResource templateUser}"/>
<DataTemplate.Triggers>
<DataTrigger Binding="{Binding Path=IsAdministrator}" Value="true">
<Setter TargetName="DynamicContent" Property="ContentTemplate" Value="{StaticResource templateAdmin}" />
</DataTrigger>
</DataTemplate.Triggers>
</DataTemplate>
</UserControl.Resources>
<Grid>
<ContentPresenter ContentTemplate="{StaticResource myTemplateSelector}"/>
</Grid>
Of course, I can seperate the Task in two further contentcontrols, but I don't want to maintain those if same content is intersecting.
So can someone suggest anything?
Best regards, and thanks in advance!

Answer 1

The simpler, the better: use a single template, which includes all the controls you need to show. Then switch their visibility using a binding to your property:
<UserControl.Resources>
<DataTemplate x:Key="myTemplate">
<Grid>
<Grid Visibility="{Binding IsAdministrator, Converter={StaticResource BooleanToVisibilityConverter}}">
<!-- Content for admin -->
</Grid>
<Grid Visibility="{Binding IsAdministrator, Converter={StaticResource NotBooleanToVisibilityConverter}}">
<!-- Content for user -->
</Grid>
</Grid>
</DataTemplate>
</UserControl.Resources>
<Grid>
<ContentPresenter ContentTemplate="{StaticResource myTemplate}"/>
</Grid>

Answer 2

Answer is to long for comment
Arnaud Weil brought me on the right way:
To access the Property 'IsAdministrator' in ViewModel from the Datatemplate, I gave the UserControl a Name e.g.:
<UserControl
x:Class="blanked out"
x:Name="this"
Used the code from Arnaud with some modifications, to inherit the Binding to the ViewModel from UserControl
<UserControl.Resources>
<BooleanToVisibilityConverter x:Key="BooleanToVisibilityConverter"/>
<helper:NotBooleanToVisibilityConverter x:Key="NotBooleanToVisibilityConverter"/>
<DataTemplate x:Key="myTemplate">
<Grid>
<Grid Visibility="{Binding DataContext.IsAdministrator, ElementName=this, Converter={StaticResource BooleanToVisibilityConverter}}">
<!-- Content for admin -->
<TextBlock Background="Yellow" Margin="3" Text="ICH BIN ADMNIN; JUCHUUU" />
</Grid>
<Grid Visibility="{Binding DataContext.IsAdministrator, ElementName=this, Converter={StaticResource NotBooleanToVisibilityConverter}}">
<!-- Content for user -->
<Image
Name="logo"
Source="/blanked out"
HorizontalAlignment="Center"
VerticalAlignment="Center" />
</Grid>
</Grid>
</DataTemplate>
</UserControl.Resources>
And for the inverted BooleanToVisibilityConverter:
using System;
using System.Globalization;
using System.Windows;
using System.Windows.Data;
namespace blankedout.Helper
{
[ValueConversion(typeof(bool), typeof(Visibility))]
public class NotBooleanToVisibilityConverter:IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
var boolValue = (bool)value;
return !boolValue ? Visibility.Visible : Visibility.Hidden;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
}
Thanks once again to Arnaud Weil
Regards