方法中的多个进程从调用线程异步执行

Question

假设我有多个（比如两个）进程，我想运行顺序但异步地进行，我该怎么做呢？请参阅下面的代码段：

public virtual Task<bool> ExecuteAsync()
{
    var tcs = new TaskCompletionSource<bool>();
    string exe1 = Spec.GetExecutablePath1();
    string exe2 = Spec.GetExecutablePath2();
    string args1 = string.Format("--input1={0} --input2={1}", Input1, Input2);
    string args2 = string.Format("--input1={0} --input2={1}", Input1, Input2);

    try
    {
        var process1 = new Process
        {
            EnableRaisingEvents = true,
            StartInfo =
            {
                UseShellExecute = false,
                FileName = exe1,
                Arguments = args1,
                RedirectStandardOutput = true,
                RedirectStandardError = true,
                WorkingDir = CaseDir
            }
        };
        var process2 = new Process
        {
            EnableRaisingEvents = true,
            StartInfo =
            {
                UseShellExecute = false,
                FileName = exe2,
                Arguments = args2,
                RedirectStandardOutput = true,
                RedirectStandardError = true,
                WorkingDir = CaseDir
            }
        };
        process1.Exited += (sender, arguments) =>
        {
            if (process1.ExitCode != 0)
            {
                string errorMessage = process1.StandardError.ReadToEndAsync();
                tcs.SetResult(false);
                tcs.SetException(new InvalidOperationException("The process1 did not exit correctly. Error message: " + errorMessage));
            }
            else
            {
                File.WriteAllText(LogFile, process1.StandardOutput.ReadToEnd());
                tcs.SetResult(true);
            }
            process1.Dispose();
        };
        process1.Start();

        process2.Exited += (sender, arguments) =>
        {
            if (process2.ExitCode != 0)
            {
                string errorMessage = process2.StandardError.ReadToEndAsync();
                tcs.SetResult(false);
                tcs.SetException(new InvalidOperationException("The process2 did not exit correctly. Error message: " + errorMessage));
            }
            else
            {
                File.WriteAllText(LogFile, process2.StandardOutput.ReadToEnd());
                tcs.SetResult(true);
            }
            process2.Dispose();
        };
        process2.Start();
    }
    catch (Exception e)
    {
        Logger.InfoOutputWindow(e.Message);
        tcs.SetResult(false);
        return tcs.Task;
    }

    return tcs.Task;
}

}

提前感谢您的想法。

编辑#1：

当我运行上面显示的代码在成功完成第一个过程后失败并出现以下错误：

"System.InvalidOperationException; An attempt was made to transition a task to a final state when it had already completed".

当我运行只有第一个进程的代码（删除与另一个进程相关的所有代码）时，它运行没问题。

Answer 1

您看到的错误与这两个进程无关。是多次设置TaskCompletionSource的SetResult方法造成的。你不能给同一个任务两个不同的结果。

有几个重要的变化：

不要仅仅因为第一个进程成功就将任务完成设置为真。你想让它等到第二个过程完成后再决定它是否真的成功了。删除 process1.Exited.
你应该只在 process1 完成后启动 process2（你说你希望它们是同步的。为此，在 process1 的 Exited 处理程序中启动 process2。另外，我假设你不想在 process1 失败时启动 process2
将 process2.Exited 处理程序移至调用 process1.Start() 的上方。这只是避免了当 process1 和 process2 在设置 process2 的 Exited 处理程序之前非常快地完成时的竞争条件。

这是未经测试的，但您的代码最终应该看起来像这样：

public virtual Task<bool> ExecuteAsync()
{
    var tcs = new TaskCompletionSource<bool>();
    string exe1 = Spec.GetExecutablePath1();
    string exe2 = Spec.GetExecutablePath2();
    string args1 = string.Format("--input1={0} --input2={1}", Input1, Input2);
    string args2 = string.Format("--input1={0} --input2={1}", Input1, Input2);

    try
    {
        var process1 = new Process
        {
            EnableRaisingEvents = true,
            StartInfo =
            {
                UseShellExecute = false,
                FileName = exe1,
                Arguments = args1,
                RedirectStandardOutput = true,
                RedirectStandardError = true,
                WorkingDir = CaseDir
            }
        };
        var process2 = new Process
        {
            EnableRaisingEvents = true,
            StartInfo =
            {
                UseShellExecute = false,
                FileName = exe2,
                Arguments = args2,
                RedirectStandardOutput = true,
                RedirectStandardError = true,
                WorkingDir = CaseDir
            }
        };
        process1.Exited += (sender, arguments) =>
        {
            if (process1.ExitCode != 0)
            {
                string errorMessage = process1.StandardError.ReadToEndAsync();
                tcs.SetResult(false);
                tcs.SetException(new InvalidOperationException("The process1 did not exit correctly. Error message: " + errorMessage));
            }
            else
            {
                File.WriteAllText(LogFile, process1.StandardOutput.ReadToEnd());
                process2.Start();
            }
            process1.Dispose();
        };

        process2.Exited += (sender, arguments) =>
        {
            if (process2.ExitCode != 0)
            {
                string errorMessage = process2.StandardError.ReadToEndAsync();
                tcs.SetResult(false);
                tcs.SetException(new InvalidOperationException("The process2 did not exit correctly. Error message: " + errorMessage));
            }
            else
            {
                File.WriteAllText(LogFile, process2.StandardOutput.ReadToEnd());
                tcs.SetResult(true);
            }
            process2.Dispose();
        };

        process1.Start();
    }
    catch (Exception e)
    {
        Logger.InfoOutputWindow(e.Message);
        tcs.SetResult(false);
        return tcs.Task;
    }

    return tcs.Task;
}

方法中的多个进程从调用线程异步执行

Multiple processes in method executed asynchronously from calling thread

c#

asynchronous

process

task