如何在 UserControl 中使用 ContentPresenter

Question

I'd like to create a UserControl (in this case a square-Button with defined Backgroundcolors) which can host it's own content.

UserControl:

<UserControl x:Class="SGDB.UI.Controls.ModernButton"
         xmlns:local="clr-namespace:SGDB.UI.Controls"
         xmlns:converter="clr-namespace:SGDB.UI.Converter"
         x:Name="_modernButton">
<Button>
    <Button.Resources>
        <converter:EnumToColorConverter x:Key="ColorConverter"/>
    </Button.Resources>
    <Button.Template>
        <ControlTemplate>
            <Border Width="{Binding Size, ElementName=_modernButton}" Height="{Binding Size, ElementName=_modernButton}" BorderBrush="Black" BorderThickness="0.8,0.8,3,3">
                <Grid Background="{Binding BackgroundColor, ElementName=_modernButton, Converter={StaticResource ColorConverter}}">
                    <ContentPresenter/>
                </Grid>
            </Border>
        </ControlTemplate>
    </Button.Template>
</Button>

Now, as you may expect it, if I use this Control inside my MainView everthing works just fine until I define some Content.

Using:

<control:ModernButton Size="200" BackgroundColor="Light">
    TEST
</control:ModernButton>

In this case "TEST" will override the whole Content of the UserControl (the whole Button Template). I guess this happens because The Button inside the UserControl is defined as "Content" itself and it will get overridden when defining new Content.

So the final question is: Is it possible to achieve what I'm looking for? if yes: How? How could I "redirect" the Content I'm defining in my MainView into the self-defined ContentPresenter inside my Button Template instead of the UserControls's ContentPresenter?

If possible I don't want to create a new dp-propery which hosts my Content, eg:

<controls:MordernButton Size="200" BackgroundColor="Light">
    <controls:ModernButton.Content>
        I don't want this, if possible
    </controls:ModernButton.Content>
</controls:ModernButton>

Answer 1

Use the ContentPropertyAttribute to instruct the xaml to set this property instead of the actual Content property.

[ContentProperty("InnerContent")]
public partial class ModernButton : UserControl
{
    public ModernButton()
    {
        InitializeComponent();
    }

    public static readonly DependencyProperty InnerContentProperty =
        DependencyProperty.Register("InnerContent", typeof(object), typeof(ModernButton));

    public object InnerContent
    {
        get { return (object)GetValue(InnerContentProperty); }
        set { SetValue(InnerContentProperty, value); }
    }
}

Then in your xaml, Bind the Content Presenter to use InnerContent property instead.

<ContentPresenter Content="{Binding InnerContent, ElementName=_modernButton}"/>

This way you can do the following without replacing the actual content.

<control:ModernButton Size="200" BackgroundColor="Light">
    TEST
</control:ModernButton>

Answer 2

Here we go.

<UserControl x:Class="SGDB.UI.Controls.ModernButton"
     xmlns:local="clr-namespace:SGDB.UI.Controls"
     xmlns:converter="clr-namespace:SGDB.UI.Converter"
     x:Name="_modernButton">

    <UserControl.Template>
        <ControlTemplate TargetType="UserControl">
            <Button Content="{TemplateBinding Content}">
                 <Button.Resources>
                    <converter:EnumToColorConverter x:Key="ColorConverter"/>
                  </Button.Resources>
            <Button.Template >
                <ControlTemplate TargetType="Button">
                    <Border Width="{Binding Size,
                                    ElementName=_modernButton}"
                    Height="{Binding Size,
                                     ElementName=_modernButton}"
                    BorderBrush="Black"
                    BorderThickness="0.8,0.8,3,3">
                        <Grid Background="{Binding BackgroundColor, ElementName=_modernButton, Converter={StaticResource ColorConverter}}">
                            <ContentPresenter />
                        </Grid>
                    </Border>
                </ControlTemplate>
            </Button.Template>
            </Button>
        </ControlTemplate>
    </UserControl.Template>
</UserControl>

Answer 3

Let's assume that youre UserControl is:

<UserControl x:Class="QuickAndDirtyAttempt.Decorator" ....
      <UserControl.Template>
        <ControlTemplate TargetType="{x:Type local:Decorator}">
          <StackPanel Orientation="Vertical">
            <Label>Foo</Label>
            <ContentPresenter/>
            <Label>Bar</Label>
          </StackPanel>
        </ControlTemplate>
      </UserControl.Template>
</UserControl>

Note the TargetType property on the template: without it the project will happily compile, but the ContentPresenter will not work. And then:

<Window ... >
    <StackPanel Orientation="Vertical">
        <local:Decorator>
            <Label Background="Wheat">User supplied content here</Label>
        </local:Decorator>
    </StackPanel>
</Window> 

I strongly recommend you to read this before implementing anything

Answer 4

Simple; Just circumvent and replace the UserControl's Template.

  <UserControl.Template>
        <ControlTemplate TargetType="{x:Type UserControl}">
            <Button Content="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=Content}">
                <Button.Resources>
                   <converter:EnumToColorConverter x:Key="ColorConverter"/>
                </Button.Resources>
                <Button.Template>
                    <ControlTemplate TargetType="{x:Type Button}">
                        <Border Width="{Binding Size,
                                        ElementName=_modernButton}"
                        Height="{Binding Size,
                                         ElementName=_modernButton}"
                        BorderBrush="Black"
                        BorderThickness="0.8,0.8,3,3">
                            <Grid Background="{Binding BackgroundColor, ElementName=_modernButton, Converter={StaticResource ColorConverter}}">
                                <ContentPresenter />
                            </Grid>
                        </Border>
                    </ControlTemplate>
                </Button.Template>
            </Button>
        </ControlTemplate>
    </UserControl.Template>

All a user control is (at least it terms of XAML and its template), is a Border with a ContentPresenter inside it. The ContentPresenter being the only important part, really.

So all you do is gut out its Template and feed the Content property the UserControl has into something a little different; in this case, your button.

This is the difference between making a usercontrol out of other controls, and shoving some controls into a user control. Making the usercontrol out of other controls gives you much more power.

Answer 5

My example for dialog box

<UserControl
x:Class="CyberpunkModManager.Controls.DialogBox"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:local="clr-namespace:CyberpunkModManager.Controls"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
d:DesignHeight="450"
d:DesignWidth="800"
Foreground="{StaticResource ThemeForeground}"
mc:Ignorable="d">
<UserControl.Template>
    <ControlTemplate TargetType="UserControl">
        <Grid Background="{StaticResource ThemeTransparentColor}">
            <Border
                MinWidth="400"
                Padding="12"
                HorizontalAlignment="Center"
                VerticalAlignment="Center"
                Background="{StaticResource ThemeElement}"
                CornerRadius="4">
                <ContentPresenter />
            </Border>
        </Grid>
    </ControlTemplate>
</UserControl.Template>