Nullable Types

There are two kinds of types:

• Value types such as int, double and bool.
• Reference types such as string and List<int>. All classes define reference types.

Reference types can be set to null, but value types can’t:

int x = null;    // Error

Sometimes, however, the ability to set value types to null can come in handy. In Java, in order to have a “nullable int”, you would use an Integer. C# instead offers nullable types: simply add ? to a value type. For example,

int? x = null;

Further Reading

• Official documentation
• Null-conditional operators