AvalonEdit in a WPF application with MVVM

According to this forum message, it's not possible to bind the Text property from the Avalon Editor to a simple property of a ViewModel.
Instead, you can use the Document property from the editor and bind it to a property of your ViewModel.
Here is the code for the view :

<Window x:Class="AvalonEditIntegration.UI.View"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:AvalonEdit="clr-namespace:ICSharpCode.AvalonEdit;assembly=ICSharpCode.AvalonEdit"
        Title="Window1"
        WindowStartupLocation="CenterScreen"
        Width="500"
        Height="500">
    <DockPanel>
        <Button Content="Show code"
                Command="{Binding ShowCode}"
                Height="50"
                DockPanel.Dock="Bottom" />
        <AvalonEdit:TextEditor ShowLineNumbers="True"
                               Document="{Binding Path=Document}"
                               FontFamily="Consolas"
                               FontSize="10pt" />
    </DockPanel>
</Window>

And the code for the ViewModel :

namespace AvalonEditIntegration.UI
{
    using System.Windows;
    using System.Windows.Input;
    using ICSharpCode.AvalonEdit.Document;

    public class ViewModel
    {
        public ViewModel()
        {
            ShowCode = new DelegatingCommand(Show);
            Document = new TextDocument();
        }

        public ICommand ShowCode { get; private set; }
        public TextDocument Document { get; set; }

        private void Show()
        {
            MessageBox.Show(Document.Text);
        }
    }
}