Question

When I was writing C# code a few days ago I noticed that the compiler complained that I had to cast null to a specific object.

Does this mean that null is simply an uninstantiated version of the type? Or is it a singleton value of a Null class like Java (even though it has special privileges)?

EDIT: an example of the code giving the error would be:

public String duplicate(String toDuplicate)
{
    return toDuplicate + toDuplicate;
}

public String duplicate(int? toDuplicate)
{
    String asString = toDuplicate.toString();

    return asString + asString;
}

public static int Main(string[] args)
{
    //This needs to be cast:
    duplicate(null);
    //To:
    duplicate((string)null);
}

The reason I commented on null in Java was after reading this:

There is also a special null type, the
type of the expression null, which has
no name. Because the null type has no
name, it is impossible to declare a
variable of the null type or to cast
to the null type. The null reference
is the only possible value of an
expression of null type. The null
reference can always be cast to any
reference type. In practice, the
programmer can ignore the null type
and just pretend that null is merely a
special literal that can be of any
reference type.

Found here: Is null an Object?

Answer 1

According to the MSDN description:

The null keyword is a literal that represents a null reference, one that does not refer to any object. null is the default value of reference-type variables. Ordinary value types cannot be null. However, C# 2.0 introduced nullable value types.