I have recently experimented with WPF and MDI. Last time I used the Win32 API in order to create a WPF-based child window within a WinForms-based MDI parent window. It did some more research and came up with a more sophisticated solution.

The main problem remains: WPF does not (yet) provide build-in mechanisms for classic MDI management (besides from tab pages). So in order to use MDI (in my case I want to transform a WinForms-based MDI application into a WPF-based one), it is necessary to use a WinForms-based MDI parent window. The real question is how can you create a WPF window as a "real" MDI child.

Since all efforts failed so far, I decided to use a WinForms-based child window and search for ways to embed a WPF window within that window. There is a ElementHost-Control (WinForms) which can host WPF controls within a WinForms window. I intended to create WPF windows or pages and not WPF user controls, so I kept looking. Fortunately I found the Frame-Control (WPF) which can host content such as pages and that can be hosted within other WPF controls.

So putting it all together I created:

1. WinForms MDI parent window (MDIParent)
2. WinForms MDI child window (MDIChild) with a ElementHost-Control
3. WPF user control (ucPageWrapper) embedding a Frame-Control

The following two code listings display the user control's XAML and C# code. As you can see it embeds a Frame-Control and its function "LoadContent" loads the page parameter into the frame.

<UserControl x:Class="ucPageWrapper"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" >
    <Grid>
        <Frame Name="Frame1" />
    </Grid>
</UserControl>

public partial class UcPageWrapper : UserControl
{
    public UcPageWrapper()
    {
        InitializeComponent();
    }

    public void LoadContent(Page page)
    {
        this.Frame1.Navigate(page);
    }
}

The next listing shows the MDI child's code. It creates a new instance of the ucPageWrapper and passes the page parameter to it.

public partial class MDIChild : Form
{
    public MDIChild()
    {
        InitializeComponent();
    }

    public void LoadContent(System.Windows.Controls.Page page)
        {
            UcPageWrapper control = new UcPageWrapper();
            control.LoadContent(page);
            this.elementHost1.Child = control;
        }
}

Finally the code inside the MDI parent window. It creates a sample page Page1 and passes it as a parameter to a new MDI child.

Page1 page = new Page1();

MDIChild child = new MDIChild();
child.LoadContent(page);
child.MdiParent = this;
child.Show();

Full source code can be downloaded here.