Process in C# (Open exe)

[C# Programming]

Hi Guy,
I need to open exe through C#. I am able to open exe by writing code

System.Diagnostics.Process.Start("C:\Program Files\abc\xyz.exe");
but now I need to check if it is already open then no need to run this code because it will reopen.
basically need to check whether its open or not, open only if not open....

Thanks&Regards
Shafiq...