How do you call program B, from within program A using c#

Question

Hello, I have two programs: A & B. Now I need to call A from within B and at the same time pass some parameters. I tried using Process.Start but it's not working. For example, let say I am calling prog A, that needs an input string from program B. So program B is calling A, passing the string that A needs in order to execute. I hope this is not too confusing! Thanks!