Question

I’m always surprised that even after using C# for all this time now, I still manage to find things I didn’t know about…

I’ve tried searching the internet for this, but using the ‘~’ in a search isn’t working for me so well and I didn’t find anything on MSDN either (not to say it isn’t there)

I saw this snippet of code recently, what does the tilde(~) mean?

/// <summary> /// Enumerates the ways a customer may purchase goods. /// </summary> [Flags] public enum PurchaseMethod {        All = ~0,     None =  0,     Cash =  1,     Check =  2,     CreditCard =  4 } 

I was a little surprised to see it so I tried to compile it, and it worked… but I still don’t know what it means/does. Any help??

Answer 1

~ is the unary one’s complement operator — it flips the bits of its operand.

~0 = 0xFFFFFFFF = -1 

in two’s complement arithmetic, ~x == -x-1

the ~ operator can be found in pretty much any language that borrowed syntax from C, including Objective-C/C++/C#/Java/Javascript.