#208 – You Can Make Any Value Type Nullable

The ? character that indicates a nullable type is really a shortcut to the System.Nullable<T> structure, where T is the type being made nullable.  In other words, using int? is equivalent to using System.Nullable<System.Int32>.

You can make any value type nullable using the Nullable<T> syntax.  You’d typically do this for your own custom struct or enum types.

For example, assume that you have the following two custom types.

        // How I'm feeling
        public enum Mood
        {
            Crabby,
            Happy,
            Petulant,
            Elated
        }

        // A 3D point with a name
        public struct Point3D
        {
            public float X, Y, Z;
            public string Name;
        }

You can use these types as nullable types using Nullable<T>.

            Nullable<Mood> me = Mood.Crabby;
            me = null;

            Nullable<Point3D> nonPoint = null;