How to check my system is locked or not using c#?

Question

I am creating C# window application, by this I want to know system status (locked or not or sleep) by running it at random time.

Below code will not work because I am running my exe at random time and then close it, So it can't catch below event code. Can someone help me how can I check windows status in my case? 

private const int SessionLockParam = 0x7;private const int SessionUnlockParam = 0x8;