Question

I always thought that the nullable types of the .NET framework where nothing but a nice construct that the framework gave us, but wasn’t anything new added to the language itself.

That is, until today, for purposes of a demonstration, I tried to create my own Nullable struct.

I get everything I need, except the capability of doing this:

var myInt = new Nullable<int>(1);
myInt = 1;

The problem is the second statement, as I cannot, by any means, overload the assignment operator.

My question is: Is this a special case in the language where the assignment operator has an overload? If not, how would you approach making that previous example work?

Thanks!

Answer 1

The assignment is question is handled using an implicit operator declared as:

public static implicit operator Nullable<T> (T value)

This is handled without any language-specific features.

The main change to the langauge for nullable support is the ability to write this as:

 int? myInt = 1;

You could implement this in your type via:

public static implicit operator Nullable<T> (T value)
{
    return new Nullable<T>(value);
}

That being sad, there is a lot of features related to Nullable<T> the C# language and CLR does that can’t be duplicated in your code.