C# working with a called process

Question

In a C# 2008 application, I have a foreach loop that is listed below:
for each (PkgID in PkgIDs)
{
Process eProcess = new Process();
String Process_Arguments = null;
eProcess.StartInfo.UseShellExecute = false;
eProcess.StartInfo.FileName = strConsoleAppLocation;
Process_Arguments = filedirectorypath + " 7654" + PkgID;
eProcess.StartInfo.Arguments = Process_Arguments;
eProcess.Start();
eProcess.WaitForExit(1800);
eProcess = null;
Process_Arguments = null;
}
As you can see from the code I listed above I have the following questions:
1. For each iteration of the for loop I create a new process object
called eProcess and then I set eProcess = null; near the end of the loop.
Thus can you tell me if this is code or not and why? If you have better
code that I could use would you tell me what you recommend by pointing
me to some code I can use as a reference??
2. You can see that I also have the following line of code,
eProcess.WaitForExit(1800);
I have this line since the process that is being called does not seem to
complete its processing before the control is returned to this program.
Thus can you tell me the following:
a. Is the number of milliseconds that I specify a good amount? Can you tell
me why or why not?
b. Since the code is returned to this calling program before the entire
eProcess finished, can you tell me if this is a good way to wait for
the eprocess to finish? I would think there is a better way to
what for eProcess to finish. If so, is there a way to tell when the eProcess
is really finished executing?

Vulpes · Accepted Answer

Well, setting eProcess to null is pointless as it's local to the foreach loop anyway and so will be destroyed and recreated again for each iteration of the loop.
What you really need to do is to call the Process.Dispose() method. This will release the unmanaged resources which it's using immediately rather than waiting for the garbage collector to get around to it. So, I'd suggest you change the code to this:
for each (PkgID in PkgIDs)  {    Process eProcess = new Process();    eProcess.StartInfo.UseShellExecute = false;    eProcess.StartInfo.FileName = strConsoleAppLocation;    string Process_Arguments = filedirectorypath + " 7654" + PkgID;    eProcess.StartInfo.Arguments = Process_Arguments;    eProcess.Start();    eProcess.WaitForExit(1800);    eProcess.Dispose(); }
Process.WaitForExit(1800) waits for a maximum of 1800 milliseconds for the process to exit and then returns immediately even if the process hasn't finished executing.
I've no idea whether 1800 milliseconds is a suitable value or not because it depends what the process is doing and how long it should normally take to do that.
However, when you're starting multiple processes like this, I wouldn't have thought that you wanted more than two or three to be running simultaneously (if they're writing to a common file you might only want one process to be running), So - unless performance is paramount - I'd err on the high side when deciding on a time-out.
If the process still hasn't ended after a long time-out, you might also want to consider killing it (using the CloseMainWindow or Kill methods, depending on whether there's a GUI or not) in case it's stuck in an infinite loop, say.
There are two ways to wait for a process to finish - synchronously using the WaitForExit method or asynchronously using the Exited event. In view of what I've said above, I think that WaitForExit should be the best option here.