异步等待块主界面 [英] Async wait block Main UI

问题描述

我正在使用新的异步等待功能从C#中的backgroundworker升级.在下面的代码中，我尝试使用ContinueWith方法复制多个任务的执行.

I am using the new async await features to upgrade from backgroundworker in C#. In the following code I am trying to replicate the execution of multiple tasks with ContinueWith method.

        Task t1 = new Task
        (
            () =>
            {
                Thread.Sleep(10000);

                // make the Task throw an exception
                MessageBox.Show("This is T1");
            }
        );

        Task t2 = t1.ContinueWith
        (
            (predecessorTask) =>
            {

                if (predecessorTask.Exception != null)
                {
                    MessageBox.Show("Predecessor Exception within Continuation");

                    return;
                }

                Thread.Sleep(1000);
                MessageBox.Show("This is Continuation");
            },

            TaskContinuationOptions.AttachedToParent | TaskContinuationOptions.OnlyOnRanToCompletion
        );

        t1.Start();

        try
        {
           t1.Wait(); <------ Comment 
           t2.Wait(); <------ Comment 
        }
        catch (AggregateException ex)
        {
            MessageBox.Show(ex.InnerException.Message);
        }  

我的问题是，当我评论t1.wait和t2.wait时，任务未阻止UI.但是，当我取消注释t1.wait和t2.wait UI块，直到线程完成.所需的行为是在try/catch块中捕获错误而不阻塞UI.我想念什么?

My question is when I comment t1.wait and t2.wait Tasks are not blocking UI. However when I uncomment t1.wait and t2.wait UI blocks until thread is completed. The desired behavior is to catch errors in try/catch block without blocking UI. What Am I missing?

推荐答案

如果此操作在UI事件处理程序中运行，则可以将async修饰符添加到方法签名中，并将t1.Wait()更改为await t1.这将把控制权返回给UI线程，并且在Thread.Sleep完成后，将继续执行并捕获任何异常.

If this is running within a UI event handler, you can add the async modifer to the method signature and change t1.Wait() to await t1. This will return control to the UI thread, and when the Thread.Sleep has completed, the continuation will execute and any exceptions will be caught.

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