process.WaitForExit()异步

Question

我想等待一个进程完成,但process.WaitForExit()挂起我的GUI.是否有基于事件的方式,或者我是否需要生成一个线程来阻止直到退出,然后自己委托事件？

Answer 1

从.NET 4.0/C#5开始,使用异步模式表示它更好.

/// <summary>
/// Waits asynchronously for the process to exit.
/// </summary>
/// <param name="process">The process to wait for cancellation.</param>
/// <param name="cancellationToken">A cancellation token. If invoked, the task will return 
/// immediately as canceled.</param>
/// <returns>A Task representing waiting for the process to end.</returns>
public static Task WaitForExitAsync(this Process process, 
    CancellationToken cancellationToken = default(CancellationToken))
{
    var tcs = new TaskCompletionSource<object>();
    process.EnableRaisingEvents = true;
    process.Exited += (sender, args) => tcs.TrySetResult(null);
    if(cancellationToken != default(CancellationToken))
        cancellationToken.Register(tcs.SetCanceled);

    return tcs.Task;
}

用法:

public async void Test() 
{
   var process = new Process("processName");
   process.Start();
   await process.WaitForExitAsync();

   //Do some fun stuff here...
}

Answer 2

process.EnableRaisingEvents = true;
process.Exited + = [EventHandler]

Answer 3

这是一个稍微清晰的扩展方法,因为它清除了取消令牌注册和退出事件.它还处理竞争条件边缘情况,其中进程可以在它开始之后但在连接Exited事件之前结束.它使用C#7中的新本地函数语法.

public static class ProcessExtensions
{
    public static async Task WaitForExitAsync(this Process process, CancellationToken cancellationToken = default)
    {
        var tcs = new TaskCompletionSource<bool>(TaskCreationOptions.RunContinuationsAsynchronously);

        void Process_Exited(object sender, EventArgs e)
        {
             tcs.TrySetResult(true);
        }

        process.EnableRaisingEvents = true;
        process.Exited += Process_Exited;

        try
        {
            if (process.HasExited)
            {
                return;
            }

            using (cancellationToken.Register(() => tcs.TrySetCanceled()))
            {
                await tcs.Task.ConfigureAwait(false);
            }
        }
        finally
        {
            process.Exited -= Process_Exited;
        }
    }
}

Answer 4

如果你选择@MgSam答案,请注意,如果你通过了WaitForExitAsync一些CancellationToken,那将在指定的延迟后自动取消,你可以得到一个InvalidOperationException.要解决这个问题,你需要改变

cancellationToken.Register(tcs.SetCanceled);

至

cancellationToken.Register( () => { tcs.TrySetCanceled(); } );

PS:别忘了及时处理你CancellationTokenSource.

Answer 5

截至目前， Process提供了.NET5一个WaitForExitAsync。 class

await process.WaitForExitAsync( token );

Answer 6

根据此链接，WaitForExit() 方法用于使当前线程等待相关进程终止。但是，Process 确实有一个可以挂钩的 Exited 事件。

Answer 7

Ryan 解决方案在 Windows 上运行良好。在 OSX 上发生了奇怪的事情，可能是死锁tcs.TrySetResult()！有2种解决方案：

第一：

包装tcs.TrySetResult()到 Task.Run()：

    public static async Task WaitForExitAsync(this Process process, CancellationToken cancellationToken = default)
    {
        var tcs = new TaskCompletionSource<bool>();

        void Process_Exited(object sender, EventArgs e)
        {
            Task.Run(() => tcs.TrySetResult(true));
        }

        process.EnableRaisingEvents = true;
        process.Exited += Process_Exited;

        try
        {
            if (process.HasExited)
            {
                return;
            }

            using (cancellationToken.Register(() => Task.Run(() => tcs.TrySetCanceled())))
            {
                await tcs.Task;
            }
        }
        finally
        {
            process.Exited -= Process_Exited;
        }
    }

有关此内容和更多详细信息的对话： 以非阻塞方式调用 TaskCompletionSource.SetResult

第二个：

    public static async Task WaitForExitAsync(this Process process, CancellationToken cancellationToken)
    {
        while (!process.HasExited)
        {
            await Task.Delay(100, cancellationToken);
        }
    }

您可以根据您的应用程序将轮询间隔从 100 毫秒增加到更长。