How to create a WPF UserControl with NAMED content

I have a set of controls with attached commands and logic that are constantly reused in the same way. I decided to create a user control that holds all the common controls and logic.

However I also need the control to be able to hold content that can be named. I tried the following:

<UserControl.ContentTemplate>
    <DataTemplate>
        <Button>a reused button</Button>
        <ContentPresenter Content="{TemplateBinding Content}"/>
        <Button>a reused button</Button>
    </DataTemplate>
</UserControl.ContentTemplate>

However it seems any content placed inside the user control cannot be named. For example if I use the control in the following way:

<lib:UserControl1>
     <Button Name="buttonName">content</Button>
</lib:UserControl1>

I receive the following error:

Cannot set Name attribute value 'buttonName' on element 'Button'. 'Button' is under the scope of element 'UserControl1', which already had a name registered when it was defined in another scope.

If I remove the buttonName, then it compiles, however I need to be able to name the content. How can I achieve this?

The answer is to not use a UserControl to do it.

Create a class that extends ContentControl

public class MyFunkyControl : ContentControl
{
    public static readonly DependencyProperty HeadingProperty =
        DependencyProperty.Register("Heading", typeof(string),
        typeof(MyFunkyControl), new PropertyMetadata(HeadingChanged));

    private static void HeadingChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        ((MyFunkyControl) d).Heading = e.NewValue as string;
    }

    public string Heading { get; set; }
}

then use a style to specify the contents

<Style TargetType="control:MyFunkyControl">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="control:MyFunkyControl">
                <Grid>
                    <ContentControl Content="{TemplateBinding Content}"/>
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

and finally - use it

<control:MyFunkyControl Heading="Some heading!">            
    <Label Name="WithAName">Some cool content</Label>
</control:MyFunkyControl>

It seems this is not possible when XAML is used. Custom controls seem to be a overkill when I actually have all the controls I need, but just need to group them together with a small bit of logic and allow named content.

The solution on JD's blog as mackenir suggests, seems to have the best compromise. A way to extend JD's solution to allow controls to still be defined in XAML could be as follows:

    protected override void OnInitialized(EventArgs e)
    {
        base.OnInitialized(e);

        var grid = new Grid();
        var content = new ContentPresenter
                          {
                              Content = Content
                          };

        var userControl = new UserControlDefinedInXAML();
        userControl.aStackPanel.Children.Add(content);

        grid.Children.Add(userControl);
        Content = grid;           
    }

In my example above I have created a user control called UserControlDefinedInXAML which is define like any normal user controls using XAML. In my UserControlDefinedInXAML I have a StackPanel called aStackPanel within which I want my named content to appear.

Another alternative I've used is to just set the Name property in the Loaded event.

In my case, I had a rather complex control which I didn't want to create in the code-behind, and it looked for an optional control with a specific name for certain behavior, and since I noticed I could set the name in a DataTemplate I figured I could do it in the Loaded event too.

private void Button_Loaded(object sender, RoutedEventArgs e)
{
    Button b = sender as Button;
    b.Name = "buttonName";
}

Sometimes you might just need to reference the element from C#. Depending on the use case, you can then set an x:Uid instead of an x:Name and access the elements by calling a Uid finder method like Get object by its Uid in WPF.

You can use this helper for set name inside the user control:

using System;
using System.Reflection;
using System.Windows;
using System.Windows.Media;
namespace UI.Helpers
{
    public class UserControlNameHelper
    {
        public static string GetName(DependencyObject d)
        {
            return (string)d.GetValue(UserControlNameHelper.NameProperty);
        }

        public static void SetName(DependencyObject d, string val)
        {
            d.SetValue(UserControlNameHelper.NameProperty, val);
        }

        public static readonly DependencyProperty NameProperty =
            DependencyProperty.RegisterAttached("Name",
                typeof(string),
                typeof(UserControlNameHelper),
                new FrameworkPropertyMetadata("",
                    FrameworkPropertyMetadataOptions.None,
                    (d, e) =>
                    {
                        if (!string.IsNullOrEmpty((string)e.NewValue))
                        {
                            string[] names = e.NewValue.ToString().Split(new char[] { ',' });

                            if (d is FrameworkElement)
                            {
                                ((FrameworkElement)d).Name = names[0];
                                Type t = Type.GetType(names[1]);
                                if (t == null)
                                    return;
                                var parent = FindVisualParent(d, t);
                                if (parent == null)
                                    return;
                                var p = parent.GetType().GetProperty(names[0], BindingFlags.Instance | BindingFlags.Public | BindingFlags.SetProperty);
                                p.SetValue(parent, d, null);
                            }
                        }
                    }));

        public static DependencyObject FindVisualParent(DependencyObject child, Type t)
        {
            // get parent item
            DependencyObject parentObject = VisualTreeHelper.GetParent(child);

            // we’ve reached the end of the tree
            if (parentObject == null)
            {
                var p = ((FrameworkElement)child).Parent;
                if (p == null)
                    return null;
                parentObject = p;
            }

            // check if the parent matches the type we’re looking for
            DependencyObject parent = parentObject.GetType() == t ? parentObject : null;
            if (parent != null)
            {
                return parent;
            }
            else
            {
                // use recursion to proceed with next level
                return FindVisualParent(parentObject, t);
            }
        }
    }
}

and your Window or Control Code Behind set you control by Property:

 public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

    }

    public Button BtnOK { get; set; }
}

your window xaml:

    <Window x:Class="user_Control_Name.MainWindow"
            xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
            xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
            xmlns:test="clr-namespace:user_Control_Name"
            xmlns:helper="clr-namespace:UI.Helpers" x:Name="mainWindow"
            Title="MainWindow" Height="350" Width="525">
        <Grid>
            <test:TestUserControl>
                <Button helper:UserControlNameHelper.Name="BtnOK,user_Control_Name.MainWindow"/>
            </test:TestUserControl>
            <TextBlock Text="{Binding ElementName=mainWindow,Path=BtnOK.Name}"/>
        </Grid>
    </Window>

UserControlNameHelper get your control name and your Class name for set Control to Property.