Question

I’m using reflection to iterate through the properties of objects. For Nullable<> types, the type is being returned correctly using the PropertyType property. However, when I invoke the property getter (either via PropertyType.GetGetMethod().Invoke(obj, new object[0]) or PropertyType.GetValue(obj, null), the result’s type is the unwrapped primitive, not Nullable<>. For reason’s I’d rather not go into, I need to convert this result into its Nullable<> type. This throws an InvalidCastException in such cases:

Convert.ChangeType(property.GetValue(obj, null), property.PropertyType);

Is there another way to ensure the property value’s type is always the same as the property’s type?

Answer 1

You cannot do that in reflection code, because in reflection code you are talking about object, and there is no such thing as a boxed Nullable<T> – it is either the boxed underlying value, or a null.

If you know the actual type, you can use the constructor to create a wrapped value, but it must only be assigned to a typed field/variable that is Nullable<T> – not object – else the CLI unwraps it again.

However, for that same reason, you don’t need it wrapped when using reflection; any code like SetValue will accept object, and will do the right thing; regardless of whether it is null or a boxed underlying value, it will be handled correctly.

Basically, the CLI has special handling when boxing and unboxing Nullable<T> that makes the question void.