How to turn off monitor screen

Found a small program called Turn Off Monitor, decided to investigate how it works.

 Used IDA to open it, turned out to be a .NET exe. Opened it using Dotnet IL Editor instead.

Main code:


Seems like the only API call needed is SendMessage. ldc.i4.m1 means push -1 to stack, so the API call is SendMessage(-1,a,b,2).

SendMessage belongs to user32.dll:


Second argument, a is 0x04000003:


Third argument, b is 0x04000004:


So the only API call needed turned out to be user32!SendMessage(-1,0x04000003,0x04000004,2).