Possible Duplicate:
Why are C# 3.0 object initializer constructor parentheses optional?
What is the difference between instatiating an object by using
classInstance = new Class() { prop1 = "", prop2 = "" };
and
classInstance = new Class { prop1 = "", prop2 = "" };
Nothing. The second is just a short-cut for the first. The first allows you to include arguments to a constructor. So, you can’t use the short-cut if the class doesn’t have an empty constructor.
You may have an interest in this question:
Why are C# 3.0 object initializer constructor parentheses optional?
And Eric Lippert´s great blog post:
Ambiguous Optional Parentheses, Part One