We , who deal with database , always complained how we cannot assign NULL to a value type variable in C#. Somewhere in Microsoft Labs someone heard out prayers and C# 2.0 came up with system.Nullable<T>. A way in which we can assign NULL to C# variable and then check if the variable HasValue or not and if it does than what is the Value.

Here is a small C# 2.0 console application that shows how to declare and varibale as NULLBALE and use functions "HasValue" and "value"

 

 

 

 

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

 

namespace PracticeSamples

{

    class Program

    {

        static void Main(string[] args)

        {

            ///

            /// system.Nullable <T> helps a value type being used a reference type

            ///

 

            //int i = null; //This will throw an error here. So what if I want to assign NULL to some var

            Nullable <int> j = null;//Does not throw Error

            Console.WriteLine("Value of J ="+j);

 

            ///

            /// declaring a varibale a Nullable swithes on Hasvalue and Value function

            ///

            Nullable<bool> k = null;//Does not throw Error

            k = true;

            if (k.HasValue)//You can do this to check if the variable has been assigned or not

            {

                Console.WriteLine("Value of K =" + k.Value);

            }

            else

            {

                Console.WriteLine("K has not been assigned any value and is NULL");

 

            }

 

           

        }

    }

}

Output is : = Value of K = True

Now we understand what  a NULLABLE type is and how to declare a value type variable as NULLABLE and how to use HasValue and Value function of a NULLABLE type variable .

 

Hope this helps someone