Execute.cs

using System;
using System.Threading;

namespace MagicUI.Framework
{
    public static class Execute
    {
        [ThreadStatic]
        private static bool _isUiThread;

        private static Action<Action> _onUiExec = action => action();

        public static void OnUi(Action action)
        {
            _onUiExec(action);
        }

        public static void SetUiContext(SynchronizationContext synchronizationContext)
        {
            _onUiExec = action =>
            {
                if (_isUiThread)
                    action();
                else
                    synchronizationContext.Send(e => action(), null);
            };

            OnUi(() => _isUiThread = true);
        }
    }
}

NotifiesOfPrepertyChangeOnUiThread.cs

using System.ComponentModel;

namespace MagicUI.Framework
{
    public class NotifiesOfPropertyChangeOnUiThread : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged = delegate { };

        protected virtual void NotifyPropertyChanged(string propertyName)
        {
            Execute.OnUi(() => PropertyChanged(this, new PropertyChangedEventArgs(propertyName)));
        }
    }
}

Program.cs

        public void Run()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);

            var rootWindow = new Window();

            // NOTE: Must be after the first form is created
            Execute.SetUiContext(SynchronizationContext.Current);

            var rootViewModel = CreateRootViewModel();

            rootWindow.SetViewModel(rootViewModel);

            Application.Run(rootWindow);
        }