Why is the string nullified?

Question

Possible duplicate:
The type string must be a non-empty type in order to use it as the T parameter in the generic type or method 'System.Nullable <T>

As the title says, why are the default strings in C # the default, but if I want, for example, ints or doubles to be null, should I explicitly say this?

Answer 1

Since the string is a reference type, the output from object and [most] other types by default are value types that implicitly output from System.ValueType;