Accesing the Tag Element from Content Control and access it inside the Data Template

Question

I have a ContentControl where I am setting its content to a DataTemplate. I am setting the Tag value of the ContentControl. Is there a way to access this Tag Element in the Data Template and pass it as CommandParameter. In other words I am trying to pass the Tag as a parameter to the DataTemplate. Please help.

   <DataTemplate x:Key="SensorStatusControlTemplate" x:DataType="viewModel:SensorBufferState">
                <Grid>
                    <Rectangle x:Name="SensorRectangle"
                               Fill="{x:Bind Converter={StaticResource SensorStateOverflowConverter},
ConverterParameter={What do I say here to get the Tag}}"
                               Height="30"
                               Width="125" />
                    <TextBlock x:Name="SensorTextBlock"
                               Text="{x:Bind Converter={StaticResource SensorStateOverflowConverter}}"
                               FontSize="{StaticResource FontSizeMedium}"
                               HorizontalAlignment="Center"
                               VerticalAlignment="Center"
                               Foreground="White" />
                </Grid>
            </DataTemplate>

Here is my ControlTemplate. Is there a way to access the Tag in the DataTemplate?

<ContentControl Content="{Binding VmPRWControlData.OverflowSensorState,UpdateSourceTrigger=PropertyChanged}"
                                        ContentTemplate="{StaticResource SensorStatusControlTemplate}"
                                        Tag="Overflow"
                                        HorizontalAlignment="Center"
                                        Width="{Binding ElementName=LABLidSensorTextBlock,Path=ActualWidth}" />

Edit: I have tried doing like this but the parameter value is null,

ConverterParameter={Binding Tag, RelativeSource={RelativeSource Mode=TemplatedParent}}

Have you tried `TemplateBinding` or `{Binding RelativeSource=TemplateParent}`? — Tanveer Badar, Oct 27 '20 at 18:15

BionicCode · Accepted Answer · 2020-10-27T19:11:02.613

You should traverse the tree to find the parent control using RelativeSource.AncestorType:

<DataTemplate DataType="{x:Type viewModel:SensorBufferState}">
  <Button CommandParameter="{Binding RelativeSource={RelativeSource AncestorType=ContentControl}, Path=Tag}"/>
</DataTemplate>

As you correctly mentioned UWP doesn't support RelativeSource.AncestorType.

The following solutions work with WPF too:

Solution 1

You can use Binding.ElementName instead

App.xaml

<DataTemplate x:Key="DataTemplate">
  <Button CommandParameter="{Binding ElementName=ContentControl, Path=Tag}"/>
</DataTemplate>

MainPage.xaml

<ContentControl x:Name="ContentControl" 
                Tag="123"  
                ContentTemplate="{StaticResource DataTemplate}" />

Solution 2

Or alternatively use the DataContext set to a view model or a DependencyProperty instead of the Tag property:

App.xaml

<DataTemplate x:Key="DataTemplate">
  <Button CommandParameter="{Binding CommandParameterValue}"/>
</DataTemplate>

MainPage.xaml.cs

public sealed partial class MainPage : Page
{
  public static readonly DependencyProperty CommandParameterValueProperty = DependencyProperty.Register(
    "CommandParameterValue",
    typeof(string),
    typeof(MainPage),
    new PropertyMetadata(default(string)));

  public string CommandParameterValue 
  { 
    get => (string) GetValue(MainPage.CommandParameterValueProperty); 
    set => SetValue(MainPage.CommandParameterValueProperty, value); 
  }

  public MainPage()
  {
    this.InitializeComponent();
    this.DataContext = this;
    this.CommandParameterValue = "ABC";
  }
}

MainPage.xaml

<ContentControl ContentTemplate="{StaticResource DataTemplate}" />

Thank you so much for the help. I will accept the answer. But the problem in my case is UWP doesn't have Ancestor Type. :( — nikhil, Oct 27 '20 at 18:26
Ahh, that's true. Let me provide an alternative solution for UWP... — BionicCode, Oct 27 '20 at 18:43
I was also searching and tried something like on this post https://stackoverflow.com/questions/37972934/uwp-equivalent-function-to-findancestor-in-uwp. But no luck — nikhil, Oct 27 '20 at 18:53
Can you please help me with this post, https://stackoverflow.com/questions/65570025/getting-a-binding-path-exception-inside-of-a-data-template — nikhil, Jan 04 '21 at 21:26

Accesing the Tag Element from Content Control and access it inside the Data Template

1 Answers1

Solution 1

Solution 2

Linked