C# program call a second program

Question

I am having a C# 2010 windows application call another C# 2008 windows application with the following code:
String Process_Arguments = null;
eRPT_Process.StartInfo.UseShellExecute = false;
eRPT_Process.StartInfo.FileName = strConsoleAppLocation;
Process_Arguments = strEncryptedValue + " " + strWebServiceurl + " 1 try";
eRPT_Process.StartInfo.Arguments = Process_Arguments;
eRPT_Process.Start();
eRPT_Process.WaitForExit(1800);
Process_Arguments = null;

My question is the following line of code:
eRPT_Process.WaitForExit(1800);

If this program does not wait for the other program to finish executing, could this make the second program stay in memory for awhile?

Basically the first program calls the second program in a loop. Thus could a thread from the previous call to the second program be running at the same time that another call to the second program is running? If so, could these cause the second program to have a memory leak?
if so how would you solve this problem?

Vulpes · Answer

1. To decide how long a delay to use I'd run the second process a large number of times (at least 100) and record how long it takes to complete. You can use the System.Diagnostics.StopWatch class for this: http://msdn.microsoft.com/en-gb/library/system.diagnostics.stopwatch(VS.100).aspx I'd then use the longest run time plus a margin (depending on the dispersion of the results) of at least 20%. 2. There are some resources (such as databases) where creating multiple simultaneous connections is not usually a problem. Similarly web services can generally deal with multiple simultaneous client requests. However other resources such as files can give you problems if multiple applications are trying to access them at the same time and even if a file allows shared access it may not be safe for multiple applications to be changing it concurrently i.e. it may not give the results you expect. You really need to consider each resource on its merits as there are no hard and fast rules on this.

Sie Ste · Answer

I have the following additional comments: 1. How long of a time delay would you use? The second application was not setup to have more than one thread running at a time. 2. For your comment  If the second process is being started in a loop it's also possible that there may be several instances of it executing in memory at the same time. If these instances are concurrently using the same resource and this resource cannot be safely shared this could obviously give you a problem. Can you explain this more? What do you mean the resources can not be shared? The applications read and write to the same database and call the same web application. Can this be an issue? If so can you explain how to solve this problem?

Vulpes · Answer

Once the second process has been launched the first process has no further influence over it. This statement: eRPT_Process.WaitForExit(1800); will cause the first process to wait (i.e. suspend execution) until the second process has ended or 1800 milliseconds has elapsed whichever occurs first. The first process will then recommence normal execution. So yes it's possible that the second process will not have finished executing when the first process restarts execution. If the second process is being started in a loop it's also possible that there may be several instances of it executing in memory at the same time. If these instances are concurrently using the same resource and this resource cannot be safely shared this could obviously give you a problem. If you've been having problems of this nature and you want to be reasonably sure that the second process will have ended before it's started again I'd use a longer (or even infinite) delay.