using System;

​

/*

Value Types cannot be null. A boolean, for example, can either be true or false.

We may want to use nullables, for example to map empty values inside a database.

*/

public class Program

{

    public static void Main()

    {

        // DateTime date = null; // This won't compile, DateTime can't be null.

        Nullable<DateTime> date = null;

        Console.WriteLine("GetValueOrDefault(): " + date.GetValueOrDefault());

        Console.WriteLine("Has value: " + date.HasValue);

        // Console.WriteLine("Value: " + date.Value); // This won't work, that's why GetValueOrDefault() is safer.

        DateTime? date2 = null; // Another way to create nullable is using question mark.

        DateTime date3 = date2.GetValueOrDefault(); // We can use GetValueOrDefault() to store a nullable inside a not-nullable.

        // Null Coalescing Operator (??):

        if (date != null)

            date2 = date.GetValueOrDefault();

        else

            date2 = DateTime.Today;

        Console.WriteLine("Variable date2: " + date2);

        // Same as above in one line:

        DateTime? date4 = null;

        DateTime date5 = date4 ?? DateTime.Today; // If date4 has value, Null Coalescing Operator assigns it to date5, otherwise use DateTime.Today;

        // Same with ternary conditional operator:

        DateTime date6 = (date4 != null) ? date.GetValueOrDefault() : DateTime.Today; // (IF THIS IS TRUE) ? EXECUTE THIS : OTHERWISE THIS

    }

}