DispatcherHelper是MVVM Light用于解决线程内修改UI界面绑定值的一个工具类，常用于解决在线程内修改了值后界面需要实时的做出响应的情况。但是由于Mvvm Light对于.net 5.0的支持时间还比较短，这个类就包含没有在MVVMLightLibsStd10中。之前解决的方法都是尽量避免在线程中修改界面参数。

直到今天在博客看到有人直接把MvvmLightLibs中，DispatcherHelper类源码直接搬到了项目中，并且可以直接使用，特此记录，以供查阅。

using System;
using System.Text;
using System.Windows.Threading;
namespace WpfApp1.Common
{
    /// <summary>
    /// Helper class for dispatcher operations on the UI thread.
    /// </summary>
    public static class DispatcherHelper
    {
        /// <summary>
        /// Gets a reference to the UI thread's dispatcher, after the
        /// <see cref="M:GalaSoft.MvvmLight.Threading.DispatcherHelper.Initialize" /> method has been called on the UI thread.
        /// </summary>
        public static Dispatcher UIDispatcher { get; private set; }
        /// <summary>
        /// Executes an action on the UI thread. If this method is called
        /// from the UI thread, the action is executed immendiately. If the
        /// method is called from another thread, the action will be enqueued
        /// on the UI thread's dispatcher and executed asynchronously.
        /// <para>For additional operations on the UI thread, you can get a
        /// reference to the UI thread's dispatcher thanks to the property
        /// <see cref="P:GalaSoft.MvvmLight.Threading.DispatcherHelper.UIDispatcher" /></para>.
        /// </summary>
        /// <param name="action">The action that will be executed on the UI
        /// thread.</param>
        public static void CheckBeginInvokeOnUI(Action action)
        {
            if (action == null)
                return;
            DispatcherHelper.CheckDispatcher();
            if (DispatcherHelper.UIDispatcher.CheckAccess())
                action();
            else
                DispatcherHelper.UIDispatcher.BeginInvoke((Delegate)action);
        }
        private static void CheckDispatcher()
        {
            if (DispatcherHelper.UIDispatcher == null)
            {
                StringBuilder stringBuilder = new StringBuilder("The DispatcherHelper is not initialized.");
                stringBuilder.AppendLine();
                stringBuilder.Append("Call DispatcherHelper.Initialize() in the static App constructor.");
                throw new InvalidOperationException(stringBuilder.ToString());
            }
        }
        /// <summary>Invokes an action asynchronously on the UI thread.</summary>
        /// <param name="action">The action that must be executed.</param>
        /// <returns>An object, which is returned immediately after BeginInvoke is called, that can be used to interact
        /// with the delegate as it is pending execution in the event queue.</returns>
        public static DispatcherOperation RunAsync(Action action)
        {
            DispatcherHelper.CheckDispatcher();
            return DispatcherHelper.UIDispatcher.BeginInvoke((Delegate)action);
        }
        /// <summary>
        /// This method should be called once on the UI thread to ensure that
        /// the <see cref="P:GalaSoft.MvvmLight.Threading.DispatcherHelper.UIDispatcher" /> property is initialized.
        /// <para>In a Silverlight application, call this method in the
        /// Application_Startup event handler, after the MainPage is constructed.</para>
        /// <para>In WPF, call this method on the static App() constructor.</para>
        /// </summary>
        public static void Initialize()
        {
            if (DispatcherHelper.UIDispatcher != null && DispatcherHelper.UIDispatcher.Thread.IsAlive)
                return;
            DispatcherHelper.UIDispatcher = Dispatcher.CurrentDispatcher;
        }
        /// <summary>
        /// Resets the class by deleting the <see cref="P:GalaSoft.MvvmLight.Threading.DispatcherHelper.UIDispatcher" />
        /// </summary>
        public static void Reset()
        {
            DispatcherHelper.UIDispatcher = (Dispatcher)null;
        }
    }
}