Nullable Integer in C#

I was working on a codeblock yesterday , and suddenly there was an integer value assigned in the  fashion as stated below

int? FileId=null;

This kindof got me going on google to look for what it actually meant.. After reading bits and pieces about this . I tried to write a code which will help me understand the use of it.

The code is as follows

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.UI;

using System.Web.UI.WebControls;

public partial class _Default : System.Web.UI.Page

{

    protected void Page_Load(object sender, EventArgs e)

    {

        int? number = null;

        if (number.HasValue == true)

        {

            Response.Write("The value is Something ");

      }

        else

        {

            Response.Write("The value is Nothing ");

        }

    }

}

So what happens when we run this particular C# Snippet .. It displays me “The value is Nothing ‘ as my output .

Now how do I get this ? Well  you see we have int? number=null;  assigned . Here int? means nullable type of integer Datatype , which can allow null values . This can be very useful when working with Databases where we have a coloumn which store null values .

Now consider I Change my logic a bit to have my number value as 5000  

        int? number = 5000;

Here the output would now be “The Value  is Nothing “