C# 0 The Complete Reference

null

, a 

System.InvalidOperationException

 will be thrown. It is also 

possible to obtain the value of a nullable instance by casting it into its underlying type.

The following program puts together the pieces and demonstrates the basic mechanism 

that handles a nullable type:

// Demonstrate a nullable type.

using System;

class NullableDemo {

  static void Main() {

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    int? count = null;

    if(count.HasValue)

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

    else

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

    count = 100;

    if(count.HasValue)

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

    else

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

  }

}

The output is shown here:

count has no value

count has this value: 100