WPF - Hosting content inside a UserControl

Question

I'm trying to create a user control that has a Grid with two rows. the first row for a title and the second one for a content that will be defined outside the user control such as a Button in our example.

Somehow I didn't get it to work.

UserControl1 xaml:

  <Grid Background="LightBlue">
    <Grid.RowDefinitions>
        <RowDefinition Height="50" />
        <RowDefinition Height="*" />
    </Grid.RowDefinitions>
    <TextBlock Text="Title" FontSize="30" Margin="10,0,0,0"/>
</Grid>

MainWindow xaml:

 <Grid>
    <local:UserControl1>
        <Button>Click me</Button>
    </local:UserControl1>
</Grid>

The picture below should explain what's my problem:

Martial

Answer 1

The following code

<local:UserControl1>
    <Button>Click me</Button>
</local:UserControl1>

Means that you set UserControl1's Content property to be that button. This button simply replaces that UserControls1's markup. So all the things that you have in UserControl1.xaml are not there any more.

EDIT

If you want your UserControl to host some markup that will be set somewhere outside of it, you can add a DependencyProperty to it, for example:

    /// <summary>
    /// Gets or sets additional content for the UserControl
    /// </summary>
    public object AdditionalContent
    {
        get { return (object)GetValue(AdditionalContentProperty); }
        set { SetValue(AdditionalContentProperty, value); }
    }
    public static readonly DependencyProperty AdditionalContentProperty =
        DependencyProperty.Register("AdditionalContent", typeof(object), typeof(UserControl1),
          new PropertyMetadata(null));

And add some element to it's markup to host that additional content. Here's an example extending the markup you provided:

<UserControl ... Name="userControl">
    <Grid Background="LightBlue">
        <Grid.RowDefinitions>
            <RowDefinition Height="50" />
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>

        <TextBlock Text="Title" FontSize="30" Margin="10,0,0,0"/>
        <ContentPresenter Content="{Binding AdditionalContent, ElementName=userControl}" />
    </Grid>
</UserControl>

Now you can use it as following:

<local:UserControl1>
    <local:UserControl1.AdditionalContent>
        <Button>Click me</Button>
    </local:UserControl1.AdditionalContent>
</local:UserControl1>

Cassatt

Why use an additional dependency property and not just replace the Control Template and bind to the content property? – Snowstorm

I agree with you. I saw your answer just after I've posted mine. It was me voting your's up – Cassatt

The explanation of why it's not working is great, but I found @blindmeis's answer to be more helpful. – Agitate

Instead of using <local:UserControl1.AdditionalContent> you can simply use [ContentProperty("AdditionalContent")] attribute on the class and then it's possible to have custom controls just inside the control's content. This is great, because no one can destroy it by accidentally setting the content instead of the AdditionalContent. – Nonillion

Thank you. Your code helped me to built usercontrol that host other control but content of the ContentPresenter not inheriting FontSize property. I have posted a question #33658862 – Psychobiology

Have a look at blindmeis's answer. You could use TemplateBinding to set ContentPresenter's Content, FontSize etc. – Cassatt

@OndrejJanacek that really should be the accepted answer. It gracefully avoids all thye gotchas from some of the workarounds suggested here. – Angelynanger

This solution works great, except for the fact that you cannot name the elements inside the user control. So naming the Button in the above example would throw an error. – Copperas

What is CalibrationPoint? The intellisence couldn't find a possible resolution to that class, is it some custom thing? [[ EDIT ]] sorry I didn't check the method Register parameters. I think this should be changed to UserControl1 to compile. – Irate

This is great! How would you do this for multiple elements in AdditionalContent? (If possible, I'd rather change the property to allow multiple items than change the usage of the usercontrol) – Partin

Answer 2

You have to set the ControlTemplate:

<UserControl>
<UserControl.Resources>
    <Style TargetType="{x:Type local:UserControl1}">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type local:UserControl1}">
                    <Grid Background="LightBlue">
                        <Grid.RowDefinitions>
                            <RowDefinition Height="50" />
                            <RowDefinition Height="*" />
                        </Grid.RowDefinitions>
                        <TextBlock Grid.Row="0" Text="Title" FontSize="30" Margin="10,0,0,0"/>
                        <ContentPresenter Grid.Row="1" />
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</UserControl.Resources>
</UserControl>

Marin

Is there a reason why you set it via UserControl.Resources/Style instead of just putting the ControlTemplate as content of UserControl.Template? – Ridgway

Unfortunately, it looks like setting the Template property of a UserControl isn't supported: social.msdn.microsoft.com/forums/silverlight/en-US/… – Lafollette

UserControl.Template works for me. I use TargetType="{x:Type UserControl}". – Delldella

Thank you for this. – Banyan

Setting the control template disables the use of x:Name within any content you set. Tested in a .Net 4.7 wpf app. Namescope is already set apparently. – Angelynanger

Answer 3

You can template the user control to add additional visuals like the TextBlock.

<UserControl>
<UserControl.Style>
  <Style TargetType="{x:Type UserControl}">
    <Setter Property="Template">
      <Setter.Value>
        <ControlTemplate>              
          <Grid Background="LightBlue"> 
          <Grid.RowDefinitions> 
            <RowDefinition Height="50" /> 
            <RowDefinition Height="*" /> 
          </Grid.RowDefinitions> 
          <TextBlock Text="Title" FontSize="30" Margin="10,0,0,0"/> 
          <ContentPresenter Grid.Row="1" Content="{TemplateBinding Content}"  />
          </Grid> 
        </ControlTemplate>
      </Setter.Value>
    </Setter>
  </Style>
</UserControl.Style>
<Button>
  Click me!
</Button>
</UserControl>

Snowstorm

use <ControlTemplate TargetType="{x:Type UserControl}"> to make it work in a resource dictionary – Mecklenburg

I create a new UserControl that needed to contain content. This is the only solution that seems to work properly without causig ton of other problems during implementation or down the road. E.g. @Marin solution does not show any visuals in the designer of the control itself. Only in the designer of the control where the new control is used. There is still the issue where a control set as content of the new control can't have a name attribute. – Piccoloist

Answer 4

Use template with

< ContentControl />

Instead of using Content Presenter

So place this:

<UserControl.Style>
        <Style TargetType="{x:Type UserControl}">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type UserControl}" >
                          <Grid Background="LightBlue"> 
                           <Grid.RowDefinitions> 
                            <RowDefinition Height="50" /> 
                            <RowDefinition Height="*" /> 
                          </Grid.RowDefinitions> 
                           <TextBlock Text="Title" FontSize="30" Margin="10,0,0,0"/> 

                        <ContentControl  Grid.Row="1" Content="{TemplateBinding Content}"  />

                        </Grid> 
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </UserControl.Style>

to your userControl

Marillin

Use template with ContentControl instead of using ContentPresenter - Why? – Vaientina

Better to use ContentPresenter inside templates, see https://mcmap.net/q/117115/-what-39-s-the-difference-between-contentcontrol-and-contentpresenter – Delldella

Answer 5

This is the simple general template for a user control (without using styles or properties to set the content):

<UserControl ...>
   <UserControl.Template>
       <ControlTemplate TargetType="{x:Type UserControl}">
           <!-- control contents here -->
           <ContentPresenter/><!-- outside contents go here -->
           <!-- control contents here -->
       </ControlTemplate>
   </UserControl.Template>
</UserControl>

The <ControlTemplate> represents the user control's XAML duplicated for each control.

The <ContentPresenter> is where the Content gets put when consuming the control.

Woaded