C# - 文本框不需要等到最后？

Question

我有这个代码：

private void button2_Click(object sender, EventArgs e)
{
    Cursor = Cursors.WaitCursor;
    logBox.Text += "My text";

    try
    {
        ping thing;
    }
    catch 
    { 
    }
}

如何在尝试之前显示 logBox.Text +=？实际上，需要等待线程结束才能在我的日志框中显示文本...

我不想等待应用程序执行尝试并在我单击按钮时直接显示 logBox.Text。

谢谢你的帮助。

Answer 1

您可以使用 Task.Factory 来实现。来自 docs 的示例：

using System;
using System.IO;
using System.Threading.Tasks;

public class Example
{
   public static void Main()
   {
      Task[] tasks = new Task[2];
      String[] files = null;
      String[] dirs = null;
      String docsDirectory = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);

      tasks[0] = Task.Factory.StartNew( () => files = Directory.GetFiles(docsDirectory));
      tasks[1] = Task.Factory.StartNew( () => dirs = Directory.GetDirectories(docsDirectory));

      Task.Factory.ContinueWhenAll(tasks, completedTasks => {
                                             Console.WriteLine("{0} contains: ", docsDirectory);
                                             Console.WriteLine("   {0} subdirectories", dirs.Length);
                                             Console.WriteLine("   {0} files", files.Length);
                                          } );
   }
}
// The example displays output like the following:
//       C:\Users\<username>\Documents contains:
//          24 subdirectories
//          16 files

只需将您创建的任务放入您正在使用的事件处理程序中即可。

Answer 2

将您的代码修改为：

private void button2_Click(object sender, EventArgs e)
{
    Cursor = Cursors.WaitCursor;
    logBox.Text += "My text";
    logBox.Refresh();//This will display the modifications

    try
    {
        ping thing;
    }
    catch 
    { 
    }
}

注意：

不推荐此答案解决问题的方式。这并不能真正使您的代码响应迅速，并且在某些边缘情况下也不能保证输出。一般来说，不建议使用这里推荐的方式。

使用后台线程或任务是更好的方法。其他答案中已经解释了任务方式。另外，有问题的评论也有相同的解释。

我正在复制一些评论（因为评论是第二 class 成员）：

If you want the UI thread to update before "ping thing" completes, you can't do "ping thing" on the UI thread. Do it in a Task. – 15ee8f99-57ff-4f92-890c-b56153

..........and that long-running tasks like this should generally be done on a background thread. – Cody Gray

Hanging the UI is an anti-pattern too. – 15ee8f99-57ff-4f92-890c-b56153

Any piece of code that you know is going to take at least a few seconds, should be done asynchronously so that you don't block the UI thread (you'll know when this happens because your program will freeze). Give this a read: msdn.microsoft.com/library/hh191443(vs.110).aspx – ThePerplexedOne

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