C# process code

Question

    I have questions to ask about the following C# 2008/2010 code listed below:
    Process eProcess = new Process();
    eDataContext rData = new eDataContext();
                string[] PkgIDs = rData.Trans.Select(c => c.Package_ID ).ToArray();

                foreach (string PkgID in PkgIDs)
                {

                    eProcess.StartInfo.FileName = "app1.exe";
                    eProcess.StartInfo.Arguments = "10 " + " 5" + PkgID;
                    eProcess.Start();
                    eProcess.WaitForExit();
                    eProcess.Close();
                 }

    My questions are the following:
    1. After the eProcess.WaitForExit(); line of code is finished waiting for the process to finish executing, is there a way to check for the condition code returned from the run. I basically want to see if the job that executed ran successfully. If so, can you tell me how to setup that code?
    2. Do I need the line of code "eProcess.Close();"/ Why or why not?
    3. I am basically looping thoough calls executing a process based upon values received in PkgID that is stored in a database table. Is this code good or not? Can you tell me why or why not? If the code is not good, can you tell me a better way to
write the code?

Vulpes · Answer

You certainly need to call eProcess.WaitForExit() for each iteration of the foreach loop so you know that the app has ended and you can therefore access eProcess.ExitCode. It's good practice to call Process.Close() as soon as the process is no longer needed because this releases unmanaged resources such as the process handle immediately.

Akkiraju Ivaturi · Answer

As Vulpes mentioned WaitForExit() let your component know that it has completed the execution and is exited gracefully or forcefully. But with that you will come to know the state of the process. By mistake I have added answers to your question in another post after adding the code. Hope the answers by Vulpes satisfies your questions. This is what MSDN says: This overload ensures that all processing has been completed including the handling of asynchronous events for redirected standard output. You should use this overload after a call to the WaitForExit(Int32) overload when standard output has been redirected to asynchronous event handlers. When an associated process exits (that is when it is shut down by the operation system through a normal or abnormal termination) the system stores administrative information about the process and returns to the component that had called WaitForExit () . The Process component can then access the information which includes the ExitTime  by using the Handle to the exited process. Because the associated process has exited the Handle property of the component no longer points to an existing process resource. Instead the handle can be used only to access the operating system's information about the process resource. The system is aware of handles to exited processes that have not been released by Process components so it keeps the ExitTime and Handle information in memory until the Process component specifically frees the resources. For this reason any time you call Start for a Process instance call Close when the associated process has terminated and you no longer need any administrative information about it. Close frees the memory allocated to the exited process.

Sie Ste · Answer

If I end up only running one process at a time do i need the following statements: eProcess.WaitForExit(); eProcess.Close(); I would think I can replace the two statements above with the following: eProcess = null; Do you agree? Why or why not?

Vulpes · Answer

Taking those questions in the same order 1. As you'll have gathered from Akkiraju's code you can check the process's exit code. This is an integer returned by the Main method of app1.exe to the operating system. It's usually 0 to indicate the process ended successfully but other values (such as 1) can be used to indicate that some problem occurred. If you use this form of Main() method in your console application you can return a custom code: static int Main(string[] args) { //.... return 1; // or whatever you like } 2. As you're using a single Process object and starting it multiple times resetting the arguments each time there's no need to call Process.Close() until all the iterations have ended. I'd also add this line immediately afterwards so the Process object can be garbage collected: eProcess = null; 3. Your code looks OK to me though Akkiraju has given you an alternative approach using the modern task based concurrency features of .NET 4.5 which should also work in .NET 4.0 (VS 2010).

Akkiraju Ivaturi · Answer

Try the following program in .NET 4.5: using System; using System.Collections.Concurrent; using System.Collections.Generic; using System.Diagnostics; using System.Globalization; using System.Threading.Tasks; class Program { static readonly BlockingCollection string > Collection = new BlockingCollection string >(); private static int _count = 0; static void Main() { const int maxTasks = 5; //we are going to spawn 5 processes for our example. var tasks = new List Task > { Task .Factory.StartNew(() => { for ( var i = 0; i { Collection.Add(i.ToString( CultureInfo .InvariantCulture)); //adding 5 items to the collection object. } Console .WriteLine( Spawning multiple processes completed. Now wait and see till all the jobs are completed. ); Collection.CompleteAdding(); }) }; for ( var i = 0; i { tasks.Add( Task .Factory.StartNew(UserTasks(i))); //Add new tasks } Task .WaitAll(tasks.ToArray()); // wait for completion } /// /// User Tasks method /// /// /// static Action UserTasks( int id) { // return a closure just so the id can get passed return () => { while ( true ) { string item; if (Collection.TryTake( out item -1)) { using ( Process p = new Process ()) { p.StartInfo.FileName = notepad.exe ; //p.StartInfo.Arguments = item; p.Start(); p.WaitForExit(); var exitCode = p.ExitCode; Console .WriteLine(exitCode == 0 ? {0} exited successfully!!! : {0} exited failed!!!  p.Id); } } else if (Collection.IsAddingCompleted) { break ; // exit loop } } Console .WriteLine( Consumer {0} finished  id); _count = _count + 1; if (_count == 4) { Console .ReadLine(); } }; } }