c# - 如何将IEnumerable与Process.Start的输出事件处理程序一起使用？

Question

我有以下用例。我已经从Unmanned C++中创建了一个EXE。假设在控制台上打印1-100。输出捕获到下面的输出回调中

List<int> a = new List<int>();
process.OutputDataReceived += new DataReceivedEventHandler((sender, e) =>
{ 
   a.add(Convert.ToInt(e.Data));
}

但是我想使用IEnumerable并产生e.Data的 yield 。考虑到C++ exe将拥有它自己的执行线程，因此它不会等待它提供控件。我将不得不等待执行完成。我可以捕获所有内容并准备一个列表。然后我可以一件一件地生产物品。我对您的问题是，在进程运行时，是否有任何已知的机制或方法来执行此操作？我可以在C++代码中进行哪些更改？这样我才能来回控制它？考虑此过程在C#端的一个功能下运行。

Answer 1

下一种方法可用于在外部进程运行时读取其输出:

var proc = new Process
{
    StartInfo =
    {
        FileName = "process_name.exe",
        UseShellExecute = false,
        RedirectStandardOutput = true,
    },
    // Set this property to true to enable external
    // process raise notification that is has exited.
    EnableRaisingEvents = true
};

// BlockingCollection is a thread safe producer-consumer
// collection. We use it to collect the output of the
// external process and to process it while the process
// is running.
var lines = new BlockingCollection<string>();

proc.OutputDataReceived += (s, e) =>
{
    // Here we collect the output of the external process.
    if (!string.IsNullOrEmpty(e.Data))
        lines.Add(e.Data);
};

// This event is raised when external process exits.
proc.Exited += (s, e) =>
{
    // Here we notify our BlockingCollection that no more
    // data to process is available. 
    lines.CompleteAdding();
};

proc.Start();
proc.BeginOutputReadLine();

// Here we start to process the output of the external process
// without waiting for it to exit.
// This loop iterates over the items produced by the
// BlockingCollection until method CompleteAdding is called.
// This loop is being executed while external process is
// running and finishes when the process exits.
foreach (string line in lines.GetConsumingEnumerable())
{
    Console.WriteLine(line);
}

// Here we do not need to call proc.WaitForExit(), because
// loop over lines collection finishes when proc exits.

这里是学习了解此代码示例的链接:

Process.EnableRaisingEvents

Process.Exited

BlockingCollection

BlockingCollection.CompleteAdding

BlockingCollection.GetConsumingEnumerable

为了方便起见，我们可以创建一个方法来启动外部流程，并立即返回IEnumerable对象，该对象可用于循环处理流程的输出数据:

private static IEnumerable<string> ReadOutput(string procFileName)
{
    var proc = new Process
    {
        StartInfo =
        {
            FileName = procFileName,
            UseShellExecute = false,
            RedirectStandardOutput = true,
        },
        EnableRaisingEvents = true
    };

    var lines = new BlockingCollection<string>();

    proc.OutputDataReceived += (s, e) =>
    {
        if (!string.IsNullOrEmpty(e.Data))
            lines.Add(e.Data);
    };

    proc.Exited += (s, e) =>
    {
        lines.CompleteAdding();
    };

    proc.Start();
    proc.BeginOutputReadLine();

    return lines.GetConsumingEnumerable();
}

然后，当需要运行外部进程并在输出数据可用时立即读取其输出时，可以使用此方法:

public static void Demo()
{
    foreach (string line in ReadOutput("process_name.exe"))
    {
        Console.WriteLine(line);
    }
}