C# Send argument through Process.Exited

Question

I start a process that uses process.exited to send the program instructions on what to do with the process is finished.

It works fine, But I need to send a argument to the Process_Exited() method. Something like this:

process.exited += Process_Exited(jobnumber);

But that does not work. Here is my code:

public void x264_thread(string jobnumber, string x264_argument, string audio_argument)
{
    file = new System.IO.StreamWriter("c:\\output\\current.out");
    mysqlconnect("UPDATE h264_encoder set status = 'running' where jobnumber = '" + jobnumber + "'");
    var proc = new Process();
    proc.StartInfo.FileName = "C:\\ffmbc\\ffmbc.exe";
    proc.StartInfo.Arguments = x264_argument;
    proc.StartInfo.UseShellExecute = false;
    proc.StartInfo.RedirectStandardOutput = true;
    proc.StartInfo.RedirectStandardError = true;
    proc.EnableRaisingEvents = true;
    proc.StartInfo.CreateNoWindow = true;
    proc.ErrorDataReceived += proc_DataReceived;
    proc.OutputDataReceived += proc_DataReceived;
    proc.Exited += process_Exited(JobNumber); //This is where I would like to include a argument

    proc.Start();
    proc.BeginErrorReadLine();
    proc.BeginOutputReadLine();
}

Then it goes to the process_Exited Method:

public void process_Exited(object sender, EventArgs e, string JobNumber) //This does not work. It does not pass the string JobNumber
{
    //Do Stuff
}

I would like to send the process_Exited() method an argument from the x264_thread

Answer 1

Just use a lambda:

proc.Exited += (sender, e) => process_Exited(sender, e, JobNumber);

The compiler now generates lots of IL, a hidden class and a hidden method to make it all work.

Lambdas are great for adapting signatures and passing additional state.

Answer 2

You can not change the signature of an event handler like Process.Exited but in your event handler code, you can cast sender as type Process since sender is really the instance of your original process. Now that you know the process, you could determine your JobNumber:

public void process_Exited(object sender, EventArgs e) 
{
    Process myProcess = (Process)sender;
    // use myProcess to determine which job number....
    // DoWork
}

Now, to get which job number is associated with which process, you could do this:

Put a field in your class:

private Dictionary<Process, string> _processDictionary = 
                               new Dictionary<Process,string>();

In your x264_thread method you could add an entry after you create the process:

_processDictionary.Add(proc, jobnumber);

Then in your event handler you could retrieve the value:

public void process_Exited(object sender, EventArgs e) 
{
    Process myProcess = (Process)sender;
    // use myProcess to determine which job number....
    var jobNumber = _processDictionary[myProcess];
    _processDictionary.Remove(myProcess);
    // DoWork
}