我想要写我自己的控制，调用构造函数时，会显示一个消息框。

 公共类的Class1
{
    公共Class1的（）
    {
        的ShowDialog（）;
    }
    无效的ShowDialog（）
    {
        SynchronizationContext的背景下= SynchronizationContext.Current;
        如果（背景！= NULL）
        {
            context.Post（（F）=＆GT;
            {
                MessageDialog对话框=新MessageDialog（你好！）;
                dialog.ShowAsync（）;
            }， 空值）;
        }
    }
}
 

如果我的类由一个人，写了codeS如下，UnauthorizedAccessException总是抛出 dialog.ShowAsync（）;

 无效MainPage_Loaded（对象发件人，RoutedEventArgs E）
        {

            ClassLibrary1.Class1 C1 =新ClassLibrary1.Class1（）;
            MessageDialog dialog1 =新MessageDialog（）;
            dialog1.ShowAsync（）;
        }
 

有没有一种方式来显示无一例外消息对话框？

我找到了一种方法，享受它！

 任务的ShowDialog（）
        {
            CoreDispatcher调度= Windows.ApplicationModel.Core.CoreApplication.MainView.CoreWindow.Dispatcher;
            FUNC＆LT;对象，任务和LT;布尔＆GT;＆GT;行动= NULL;
            行动=异步（0）=＆GT;
            {
                尝试
                {
                    如果（dispatcher.HasThreadAccess）
                        等待新的MessageDialog（你好！）ShowAsync（）。
                    其他
                    {
                        dispatcher.RunAsync（CoreDispatcherPriority.Normal，
                        （）=＆GT;行动（O））;
                    }
                    返回true;
                }
                赶上（UnauthorizedAccessException）
                {
                    如果（动作！= NULL）
                    {
                        Task.Delay（500）.ContinueWith（异步T =＆GT;等待行动（O））;
                    }
                }
                返回false;
            };
            返回动作（空）;
        }
 

解决方案

由于MessageDialogue需要在UI线程上运行，你可以尝试切换到：

  VAR调度= Windows.UI.Core.CoreWindow.GetForCurrentThread（）调度。
dispatcher.RunAsync（DispatcherPriority.Normal，＆LT;拉姆达为您code应该运行在UI线程＆GT的;）;
 

I Want to write my own control, when the ctor is invoked, a MessageBox is shown.

public class Class1
{
    public Class1()
    {
        ShowDialog();
    }
    void ShowDialog()
    {
        SynchronizationContext context = SynchronizationContext.Current;
        if (context != null)
        {
            context.Post((f) =>
            {
                MessageDialog dialog = new MessageDialog("Hello!");
                dialog.ShowAsync();
            }, null);
        }
    }
}

If my class is used by someone, and write the codes as below, UnauthorizedAccessException is always thrown in dialog.ShowAsync();

void MainPage_Loaded(object sender, RoutedEventArgs e)
        {

            ClassLibrary1.Class1 c1 = new ClassLibrary1.Class1();
            MessageDialog dialog1 = new MessageDialog("");
            dialog1.ShowAsync();
        }

Is there a way to show a message dialog without exception?

I found a way, enjoy it!

Task ShowDialog()
        {
            CoreDispatcher dispatcher = Windows.ApplicationModel.Core.CoreApplication.MainView.CoreWindow.Dispatcher;
            Func<object, Task<bool>> action = null;
            action = async (o) =>
            {
                try
                {
                    if (dispatcher.HasThreadAccess)
                        await new MessageDialog("Hello!").ShowAsync();
                    else
                    {
                        dispatcher.RunAsync(CoreDispatcherPriority.Normal,
                        () => action(o));
                    }
                    return true;
                }
                catch (UnauthorizedAccessException)
                {
                    if (action != null)
                    {
                        Task.Delay(500).ContinueWith(async t => await action(o));
                    }
                }
                return false;
            };
            return action(null);
        }

As MessageDialogue needs to run on the UI thread, can you try switching it to:

var dispatcher = Windows.UI.Core.CoreWindow.GetForCurrentThread().Dispatcher;
dispatcher.RunAsync(DispatcherPriority.Normal, <lambda for your code which should run on the UI thread>);