Question

Wanted a simple but efficient method to get value from Nullable when T is not known at the compile time.

So far have something like this:

public static object UnwrapNullable(object o)
{
    if (o == null)
        return null;

    if (o.GetType().IsGenericType && o.GetType().GetGenericTypeDefinition() == typeof(Nullable<>))
        return ???

    return o;
}

anything can be done here without dipping into dynamic code generation?

used on .NET 2.0

Answer 1

o can never refer to an instance of Nullable<T>. If you box a nullable value type value, you either end up with a boxed value of the non-nullable underlying type, or a null reference.

In other words, o.GetType() can never return Nullable<T> for any value of o – regardless of the type of o. For example:

Nullable<int> x = 10;
Console.WriteLine(x.GetType()); // System.Int32

Here we end up boxing the value of x because GetType() is declared on object and not overridden in Nullable<T> (because it’s non-virtual). It’s a little bit of an oddity.