C# 0 The Complete Reference

Nullable Objects in Expressions

A nullable object can be used in expressions that are valid for its underlying type. 

Furthermore, it is possible to mix nullable objects and non-nullable objects within the same 

expression. This works because of the predefined conversion that exists from the underlying 

type to the nullable type. When non-nullable and nullable types are mixed in an operation, 

the outcome is a nullable value.

The following program illustrates the use of nullable types in expressions:

// Use nullable objects in expressions.

using System;

class NullableDemo {

  static void Main() {

    int? count = null;

    int? result = null;

    int incr = 10; // notice that incr is a non-nullable type

    // result contains null, because count is null.

    result = count + incr;

    if(result.HasValue)

      Console.WriteLine("result has this value: " + result.Value);

    else

      Console.WriteLine("result has no value");

    // Now, count is given a value and result will contain a value.

    count = 100;

    result = count + incr;

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