New "var" keyword

The var keyword is a new keyword in Dot net Framework 3.5 that can infer its data type from the resulting set. Var keyword

For instance, look at the following examples:

var one = 1; //infers an int

var two = "2"; // infers a string

var three = from c in Customers select c; //infers IQueryable<Customer>

var four = customers.FirstOrDefault(); //infers Customer reference

This means full intellisense is available in VS 2008, as long as the compiler can infer the type.  The following results in a compile error:

var five = null;

because the compiler couldn't  infer the type of the variable from null. “Var” is NOT a variant, everything is known by the compiler at compile-time.

var keyword can be used in place of the type name when performing local variable declarations.  

Actually, "var" only tell the compiler to replace it with the type name by infering the type from the value we assign while initializing the variable.