Waiting for the command to complete in C#

Question

I am new to C# and trying to develop a small application which internally opens a command prompt and executes some command here. This is what I have done so far:

    m_command = new Process();
    m_command.StartInfo.FileName = @"cmd.exe";
    m_command.StartInfo.UseShellExecute = false;
    m_command.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;
    m_command.StartInfo.CreateNoWindow = true;
    m_command.StartInfo.RedirectStandardInput = true;
    m_command.StartInfo.RedirectStandardOutput = true;

    m_command.Start();

    m_reader = m_command.StandardOutput;
    m_writer = m_command.StandardInput;

    m_writer.WriteLine("Somecommand"); //execute some command

As you can see, I have redirected the input and output. My question is how do I execute the "some command" synchronously i.e. I want to read the result of my command using the redirected output. For that I have to wait until the command I invoked using WriteLine to complete. How do I do that?

Answer 1

That really depends on what the command will do. You could wait for the process to exit with Process.WaitForExit, while simultaneously reading from m_reader in another thread or with OutputDataReceived. That will only work if the process is going to quit when the command has finished though. (Note that you have to read the output, otherwise it could fill up the output buffer and basically block the process.)

The other option is if you'll get a certain bit of output when the command has finished - such as the next command prompt. The trouble is that if your command happens to output the same thing, you'll get it wrong.

It feels like launching a command prompt like this isn't a great approach though. Any reason you don't create a separate process each time?

Another option: if you can work out what process you've just launched via the command line, you could find that as a Process and wait for that to exit. It's tricky though - I really would try to redesign your solution.

Answer 2

You can call

 m_command.WaitForExit();