Question

所以我有类似的代码

private void doSmth()
{
   str = makeStr();
}
private void button_Click(object sender, EventArgs e)
{
   Task task = new Task(doSmth);
   task.Start();
   task.Wait();
   textBox.Text = str;
}

它很冷，我知道为什么会因为Wait()而发生这种情况。我试图像这样使用ContinueWith()

task.ContinueWith((t) => {textBox.Text = str;});

但抛出InvalidOperationException：

无效

调用线程无法访问此对象，因为它不同线程拥有它

我该如何解决这个问题？也许我应该完全使用另一种方法来实现我想要的东西。感谢。

Answer 1

你会想要这个：

private String DoSomething() {

    return makeStr(); // return it, don't set it to a field.
}

private async void button_Click(...) {

    String result = await Task.Run( DoSomething );
    textBox.Text = result;
}

......这相当于：

private async void button_Click(...) {

    // Task<> is the .NET term for the computer-science concept of a "promise": https://en.wikipedia.org/wiki/Futures_and_promises
    Task<String> resultPromise = Task.Run( DoSomething ); 
    String result = await resultPromise;
    textBox.Text = result;
}

...（大致）相当于：

private void button_Click(...) {

    Thread thread = new Thread( () => {

        String result = DoSomething();
        this.BeginInvoke( () => {

            this.textBox.Text = result;
        } );

    } );
    thread.Start();
}

Answer 2

首先，你必须开始任务才能等待它;）
如果要使用ContinueWith（）而不是async / await，则可以使用选项TaskContinuationOptions.ExecuteSynchronously。这将导致在调用线程中执行继续操作。

Task task = new Task(doSmth);
task.ContinueWith(t => textBox.Text = str, TaskContinuationOptions.ExecuteSynchronously);
task.Start();
//task.Wait(); // optional if you want to wait for the result

Answer 3

尝试执行此操作，它对我有用：

Task ts =new Task(new Action(()=>{
//your code here
}
));
ts.Start();//start task

//here we wait until task completed
while (!ts.IsComplete)//check until task is finished
{
//pervent UI freeze
Application.DoEvents();
}
//Task Completed
//Continue with ...
textBox.Text = ts.Result;

如何使用Task.Wait避免WinForm冻结

3 个答案: