I’ve seen many a question on stackoverflow and other places about running a process and capturing it’s output. Using the System.Diagnostics.Process correctly is not easy and most often it’s done wrong.
Some common mistakes with System.Diagnostics.Process:
- Not capturing both output streams (error & output)
- Not redirecting input can cause applications to hang
- Not closing redirected input can cause applications to hang
- Not calling BeginOutputReadLine/BeginErrorReadLine when using events
- Using OutputDataReceived/ErrorDataReceived without waiting for null
- Not checking for null in OutputDataReceived/ErrorDataReceived handlers
- Forgetting to set EnableRaisingEvents = true; when using the Exited event
- Forgetting ErrorDialog, CreateNoWindow, or UseShellExecute settings
- Incorrect handling of StandardOutput or StandardError stream readers
So with this said, here are some basic guidelines:
- Use the OutputDataReceived/ErrorDataRecieved events NOT the StandardOutput or StandardError. This will save you a lot of headache and needless thread management.
- Always capture all output AND input, if you don’t plan to provide input, close the stream immediately.
- Your process isn’t done until it exited AND you have read all the data. OutputDataReceived CAN AND WILL be fired after a call to WaitForExit() returns. You will need wait handles for each output stream and set the wait handle once your receive (null) data.
- ProcessRunner library class source code, online help, or see the usage example.
- For a clean stand-alone example see “Using Process.Start to capture console output“
- Escaping arguments: “How to correctly escape command line arguments in c#“
- Finding an Executable: “How to search the environment’s path for an exe or dll“