ContentPresenter in UserControl

Question

I'm new to WPF and I'm trying to create an UserControl which will have some nested content.

<my:InformationBox Header="General Information" Width="280">
    <StackPanel>
        <Label>Label1</Label>
        <Label>Label2</Label>
    </StackPanel>
</my:InformationBox>

As you can see I want to put a StackPanel into it. As I read some articles I am supposed to add ContentPresenter to my UserControl, so I did, but I cannot find what should be binded to it's Content property.

Here is my UserControl code

<UserControl x:Class="ITMAN.InformationBox"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             mc:Ignorable="d" 
             d:DesignHeight="200" d:DesignWidth="280" Name="infoBox" Loaded="infoBox_Loaded">
    <StackPanel Width="{Binding ElementName=infoBox, Path=Width}" HorizontalAlignment="Stretch">
        <Label Content="{Binding ElementName=infoBox, Path=Header}" />
        <Border BorderThickness="0,1,0,0" Padding="10 5" Margin="5 0 5 10" BorderBrush="#B4CEDE">
            <StackPanel>
                <ContentPresenter Content="{Binding Content}" />
                <Label Content="End" />
            </StackPanel>
        </Border>
    </StackPanel>
</UserControl>

I've tried many combinations from various articles, but I cannot find any working example of what I want to achieve.

Similiar question was asked earlier by another user, but given there answers didn't help me: Does anyone have a simple example of a UserControl with a single ContentPresenter?

Bacchus

As far as I am aware, user controls do not have a Content property. Also ContentPresenters are usually only used in templates. I think what you need to do is create a custom control with a dependency property Content and a default template that sets up your control as you did with the user control. – It might be possible to add the DP to the user control’s class instead; you would have to use a ContentControl then though. – Threemaster

Yes you need to add dependency properties to your usercontrol. Check this out codeproject.com/Articles/224230/… – Breath

@Threemaster a User control is a ContentControl, therefore a ContentPresenter is indeed useable. – Catfish

@Catfish But isn’t it a content control so you can construct a custom user control with content? Is the resulting control, the one you create from it, a content control as well? – Threemaster

@Threemaster a UserControl derives from ContentControl. The xaml part is its ControlTemplate. So you can build UserControls that won't use the Content at all, but if you want to use it, you need to use the ContentPresenter. – Catfish

@Threemaster i have to apologize, seems i was wrong. Its not the template your define in xaml, it is indeed its content. See user1537441 answer. One of the reasons i don't use UserControls at all. – Catfish

Answer 1

I solved this problem by applaying custom style to GroupBox. I've created Syle in ResourceDictionary, which looks as follows

<Style x:Key="InformationBoxStyle" TargetType="GroupBox">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="GroupBox">
                <Grid>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="Auto"/>
                        <RowDefinition Height="*"/>
                    </Grid.RowDefinitions>
                    <Label>
                        <ContentPresenter Margin="4" ContentSource="Header"
                               RecognizesAccessKey="True" />
                    </Label>
                    <Border Grid.Row="1" BorderThickness="0,1,0,0" Padding="10 5"
                               Margin="5 0 5 10" BorderBrush="#B4CEDE">
                        <StackPanel>
                            <ContentPresenter />
                        </StackPanel>
                    </Border>
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

And applied this style to GroupBox

<GroupBox Header="General Information" Width="280" Style="{StaticResource InformationBoxStyle}">
    <StackPanel>
        <Label>Label1</Label>
        <Label>Label2</Label>
    </StackPanel>
</GroupBox>

This code works as expected

You may also refer to this great article, which shows different options to achieve it: http://www.codeproject.com/Articles/82464/How-to-Embed-Arbitrary-Content-in-a-WPF-Control It also describes why ContentPresenter doesn't work in my code.

Bacchus

That codeproject link explaining the use of the ContentControl with a Template static resource instead of a style worked very well. – Christiansen

Answer 2

ContentPresenter is kind of a magic control. If you don't supply anything to it, it will automatically set the Content, ContentTemplate and ContentTemplateSelector property with a TemplateBinding to the TemplatedParent. Which means, you don't need to supply anything to it, just

<ContentPresenter/>

in your UserControl, and it should automatically use the corresponding properties found in your UserControl. Also remember that a binding like {Binding Content} always referes to your DataContext, which i guess is not what you wanted.

Catfish

I thought about it in the first place but it doesn't work neither. I will try to make it as a template. – Bacchus

well i tried it and it works perfectly fine, maybe you have some other needs that wasn't clear from your question. To be sure, you can give your Usercontrol in xaml a name like x:Name="myControl" and change your content binding to Content="{Binding ElementName=myControl, Path=Content}" and see if that works. But an empty ContentPresenter works in my test case. – Catfish

It's funny that when Im writing Content={Binding ElementName=infoBox, Path=Content}` my Visual Studio 2010 crushes every time I'm doing it – Bacchus

Try it in a very simple application. Make a new wpf project, add a user control and try it there. Maybe you have another problem in your application. – Catfish

Answer 3

You need to create a dependency property on your UserControl code behind such as InnerContent.

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

    public static readonly DependencyProperty InnerContentProperty =
        DependencyProperty.Register("InnerContent", typeof(object), typeof(ConfirmationControl), new PropertyMetadata(null));

Then you need to bind to that InnerContent on the XAML side of that UserControl.

 <ContentControl Content="{Binding InnerContent, ElementName=userControl}" />

Then when you use it instead of placing content in the UserControl directly and overwriting the existing content just add it to the InnerContent portion.

    <UserControls:InformationBox>
        <UserControls:InformationBox.InnerContent>
            <TextBlock Text="I'm in the InnerContent" />
        </UserControls:InformationBox.InnerContent>
    </UserControls:InformationBox>

Otherwise using a Template or Style is just as good but if you're wanting to package up a UserControl for use without forcing anyone to also reference a style or template this is probably one of your better options.

Sociology

I got this error message: Cannot set Name attribute value 'btMain' on element 'Button'. 'Button' is under the scope of element 'MyCustomControl', which already had a name registered when it was defined in another scope. – Doggone

@LucaZiegler I think this qualifies as a new question / issue and not a comment. Post it in the questions and add the code so someone, or myself, can help you with it please. – Sociology