XAML Binding to a FrameworkElement in a UserControl

Question

I got a custom UserControl (MyControl) with several properties (which works just fine). I want a new property that let the page using the UserControl "paste in" some content to be shown direct in the UserControl - ex. a Path. I have tried; ContentPresenter, ContentControl, StackPanel, with no luck...

MyControl.xaml

<ContentControl Grid.Column="0" Content="{Binding MyContent, ElementName=root}"></ContentControl>

MyControl.xaml.cs

public object MyContent
{
  get { return (object)GetValue(MyContentProperty); }
  set { SetValue(MyContentProperty, value); }
}

public static readonly DependencyProperty MyContentProperty =
  DependencyProperty.Register("MyContent", typeof(object), typeof(MyControl), new PropertyMetadata(null));

SomePage.xml

<mycontrols:MyControl x:Name="FavoritesButton">
  <mycontrols:MyControl.MyContent>
    <Path Data="M1540.22,2082.07L1546.95,2102.78 1568.73,2102.78 1551.11,2115.58 1557.84,2136.29 1540.22,2123.49 1522.6,2136.29 1529.33,2115.58 1511.71,2102.78 1533.49,2102.78 1540.22,2082.07z" Stretch="Uniform" Fill="#FFFFFFFF" Width="50" Height="50" Margin="30"></Path>
  </mycontrols:MyControl.MyContent>
</mycontrols:MyControl>

Answer 1

I have the following which works really well. (While it is somewhat against the principles of MVVM ... I still like to dynamically handle my user controls in a single frame area of the main window)

My MainWindow.xaml:

<!-- Main Frame -->
<Grid Grid.Column="1" Margin="10" Name="MainWindowFrameContent">
   <ItemsControl ItemsSource="{Binding Path=MainWindowFrameContent}" >

      <!-- This controls the height automatically of the user control -->
      <ItemsControl.ItemsPanel>
         <ItemsPanelTemplate>
            <UniformGrid Columns="1" IsItemsHost="True"/>
         </ItemsPanelTemplate>
      </ItemsControl.ItemsPanel>
   </ItemsControl>
</Grid>

My MainViewModel.cs:

using System;
using System.Collections.ObjectModel;
using System.Windows;
using System.Windows.Input;
using myProject.View;
using myProject.Models;

namespace myProject.ViewModel
{
    public class MainViewModel : ObservableObject
    {
        public MainViewModel() { }

        // This handles adding framework (UI) elements to the main window frame
        ObservableCollection<FrameworkElement> _MainWindowFrameContent = new ObservableCollection<FrameworkElement>();
        public ObservableCollection<FrameworkElement> MainWindowFrameContent
        {
            get { return _MainWindowFrameContent; }
            set { _MainWindowFrameContent = value; RaisePropertyChangedEvent("MainWindowFrameContent"); }
        }
    }
}

MainViewModel.cs is a "public class MainViewModel : ObservableObject". This allows me to implement "RaisePropertyChangedEvent" so that the binding will successfully update when I change the value of "MainWindowFrameContent".

My ObservableObject.cs:

using System.ComponentModel;

namespace myProject.ViewModel
{
    public class ObservableObject : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        protected void RaisePropertyChangedEvent(string propertyName)
        {
            var handler = PropertyChanged;
            if (handler != null)
                handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

Then when I want to add an item to the MainWindowFrameContent, I simply do the following within my MainViewModel.cs:

void _AddNewUserControl()
{
    myUserControl hControl = new myUserControl();
    MainWindowFrameContent.Clear(); // Clear the frame before displaying new content
    MainWindowFrameContent.Add(hControl);
}

Then you can create as many user controls as you would like. Each command you want to display can have its own void _AddNewUserControl type method in the VM and it will display to the main window. Again, its a bit contrary to the MVVM framework, but it keeps this pretty clean from a code base.

Answer 2

I got it working... The solution was as follows:

MyControl.xaml

<ContentControl Content="{Binding Shape, ElementName=root}" />

MyControl.xaml.cs

public Shape Shape
{
    get { return (Shape)GetValue(ShapeProperty); }
    set { SetValue(ShapeProperty, value); }
}

public static readonly DependencyProperty ShapeProperty =
        DependencyProperty.Register("Shape", typeof(Shape), typeof(MyControl), new PropertyMetadata(null));

SomePage.xml

<mycontrols:MyControl>
    <mycontrols:MyControl.Shape>
        <Path Data="M1540.22,2082.07L1546.95,2102.78 1568.73,2102.78 1551.11,2115.58 1557.84,2136.29 1540.22,2123.49 1522.6,2136.29 1529.33,2115.58 1511.71,2102.78 1533.49,2102.78 1540.22,2082.07z" Style="{StaticResource PathStyle}" />
    </mycontrols:MyControl.Shape>
</mycontrols:MyControl>