Hidden Features of C#? [closed]

Answer 1

I tend to find that most C# developers don't know about 'nullable' types. Basically, primitives that can have a null value.

double? num1 = null; 
double num2 = num1 ?? -100;

Set a nullable double, num1, to null, then set a regular double, num2, to num1 or -100 if num1 was null.

http://msdn.microsoft.com/en-us/library/1t3y8s4s(VS.80).aspx

one more thing about Nullable type:

DateTime? tmp = new DateTime();
tmp = null;
return tmp.ToString();

it is return String.Empty. Check this link for more details