App.xaml.cs

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Reflection;
using System.Threading.Tasks;
using System.Windows;

namespace EasyJob
{
    /// <summary>
    /// Interaction logic for App.xaml
    /// </summary>
    public partial class App : Application
    {
        protected override void OnStartup(StartupEventArgs e)
        {
            base.OnStartup(e);

            SetDropDownMenuToBeRightAligned();

        }

        private static void SetDropDownMenuToBeRightAligned()
        {
            var menuDropAlignmentField = typeof(SystemParameters).GetField("_menuDropAlignment", BindingFlags.NonPublic | BindingFlags.Static);
            Action setAlignmentValue = () =>
            {
                if (SystemParameters.MenuDropAlignment && menuDropAlignmentField != null) menuDropAlignmentField.SetValue(null, false);
            };

            setAlignmentValue();

            SystemParameters.StaticPropertyChanged += (sender, e) =>
            {
                setAlignmentValue();
            };
        }
    }
}