c# - 如何以异步方法向 UI 提供反馈？

Question

我一直在开发一个 Windows 窗体项目，我有 10 个任务要做，我想以 async 的方式来完成。当用户单击按钮时，这些任务将启动，我调用 async 方法来执行此操作。在我的代码中，我已经有了这些过程的参数列表。

我的问题是:

A) How transform my code to run all process in parallel? (I would like to implement async/await)

B) How to provide a feedback to my UI application?

下面的代码是我试过的:

我的按钮调用一个方法来启动进程

private void button1_Click(object sender, EventArgs e)
{
    // almost 15 process
    foreach (var process in Processes)
    {
        // call a async method to process
        ProcessObject(process);
    }
}

模拟我的进程获取参数的方法

private async void ProcessObject(ProcessViewModel process)
{
    // this is my loop scope, which I need to run in parallel
    {
       // my code is here

       // increment the progress of this process
       process.Progress++;

       // feedback to UI (accessing the UI controls)
       UpdateRow(process);
    }
}

我试过了，但我不确定这是否是更新我的 UI(网格)的正确方法。

private void UpdateRow(ProcessViewModel process)
{
    dataGridView1.Rows[process.Index - 1].Cells[1].Value = process.Progress;
    dataGridView1.Refresh();
}

Answer 1

Sriram 介绍了如何执行异步/等待 in his answer ，但是我想向您展示另一种方法，以他的回答为基础来更新 UI 线程上的进度。

.NET 4.5 添加了 IProgress<T> 接口(interface)和 Progress<T> 类(class)。内置的 Progress 类捕获同步上下文，就像 async/await 一样，然后当您报告进度时，它会使用该上下文进行回调(在您的例子中是 UI 线程)。

private async void button1_Click(object sender, EventArgs e)
{
     var progress = new Progress<ProcessViewModel>(UpdateRow); //This makes a callback to UpdateRow when progress is reported.

     var tasks = Processes.Select(process => ProcessObject(process, progress)).ToList();
     await Task.WhenAll(tasks);
}

private async Task ProcessObject(ProcessViewModel process, IProgress<ProcessViewModel> progress)
{
    // my code is here with some loops
    await Task.Run(()=>
    {
        //Will be run in ThreadPool thread
        //Do whatever cpu bound work here


        //Still in the thread pool thread
        process.Progress++;

        // feedback to UI, calls UpdateRow on the UI thread.
        progress.Report(process); 
    });
}