Url: http://msdn.microsoft.com/library/default.asp?u…
Interesting what can happen when you re-read the specification. I’ve been taking time in the “library” to read the 2.0 C# Specification. But instead of skiping the old stuff and concentrating on the new language stuff, I am reading the whole thing again. Something interesting I found in the ‘switch’ statement.
I am an old C++ hack from the COM days so I assumed that I knew how the switch worked:
int x = 1;
switch (x){ case 1: Console.WriteLine("1"); break; case 2: Console.WriteLine("2"); break; default: Console.WriteLine("Unknown"); break;}
Pretty basic stuff. But because of my C++ legacy, I assume that this wouldn’t work (which it does):
switch (x){ default: Console.WriteLine("Unknown"); break; case 2: Console.WriteLine("2"); break; case 1: Console.WriteLine("1"); break;}
Ok, so order isn’t that important (though I like the style of the default first). But because we don’t have fall-through like in C++, I thought that linking multiple cases was kinda hacky…of course its because I didn’t know about goto case:
switch (x){ case 1: goto default; case 2: Console.WriteLine("2"); break; case 3: goto case 2; default: Console.WriteLine("Unknown"); break;}
Look closely at two lines if you’re not familiar with it. The ‘goto default’ indicates to go to the default case; while the 'goto case 2’ says go to the code inside case 2! To further illustrate, this is what it would look like with a string switch:
string s = "3";switch (s){ case "1": goto default; case "2": Console.WriteLine("2"); break; case "3": goto case "2"; default: Console.WriteLine("Unknown"); break;}
Notice the ‘goto case “2”’ mimics the actual case label, so depending on what you’re switching on, you’d change that for your case statement. Pretty sweet.
Just don’t tell Microsoft I just learned this otherwise they might take my C# MVP away ;)
