With the advent of VS2010, there's an explosion of interest around the new features of C#4.

Named parameters.

That's a cool one.  Look at the code below and note that without checking with the signature you can't really tell where's the title and where's the message:

public void SendMessage(string title, string message) { ... }

SendMessage("foo", "boo"); //that's how you call it

And look at the C#4 variant - now it's much better, eh?

SendMessage(title: "foo", message: "boo");

The Question.

And now the question that looms in the minds of many, and ardent C# admirers knit their brows in perplexity: why do we have to use ':' for named parameters? Surely the "=" would be much better?

Well, the reason for using colons instead of equals is simple: the equal sign already has a meaning.

int myInt;

CallMe(myInt = 5);  //set myInt variable to 5

CallMe(myInt : 5);  //set myInt parameter of CallMe method to 5