Wait for multiple processes to complete

Question

I want my program to wait for all processes to finish and then delete some temporary files. I already have a block of code that can do this when dealing with one process at a time, but I can't make it work for multiple processes.

I'll start by showing the code that works. This code correctly runs a process, waits for it to finish, and then deletes the temporary file:

foreach (string script in scriptList)
{
     ProcessStartInfo myProcess = new ProcessStartInfo();
     myProcess.FileName = accoreconsolePath;
     myProcess.Arguments = "/s \"" + script + "\"";
     myProcess.CreateNoWindow = true;         
     Process myWait = Process.Start(myProcess);
     myWait.WaitForExit();

     File.Delete(script);            
}  

The above is neatly contained within the foreach loop. What I can't get working is a parallel version of this where the wait statement is outside of the foreach loop:

  Process myWait;
  foreach (string script in scriptList)
  {
     ProcessStartInfo myProcess = new ProcessStartInfo();
     myProcess.FileName = accoreconsolePath;
     myProcess.Arguments = "/s \"" + script + "\"";
     myProcess.CreateNoWindow = true;
     myWait = Process.Start(myProcess);
  }
  myWait.WaitForExit();                             //error: use of unassigned local variable "myWait"
  //delete file would go here

I think I just need to initialize myWait before going into the foreach loop, but I don't know how to do that. How do I initialize a process without assigning it to anything? Is there some other simple way to do this?

Answer 1

I would store the process handles in a dictionary of script vs process handle, and then later wait for all processes to exit. Below is the code:

var processes = new Dictionary<string,Process>();

foreach (string script in scriptList)
{
    ProcessStartInfo myProcess = new ProcessStartInfo();
     myProcess.FileName = accoreconsolePath;
     myProcess.Arguments = "/s \"" + script + "\"";
     myProcess.CreateNoWindow = true;
     myWait = Process.Start(myProcess);
     processes.Add(script, myWait);
}

foreach(var script in processes.Keys)
{
    Process process = processes[script];

    process.WaitForExit();
    process.Close();

    File.Delete(script);
}