Create Cookie ASP.NET & MVC

Question

I have a quite simple problem. I want to create a cookie at a Client, that is created by the server. I've found a lot of pages that describe, how to use it - but I always stuck at the same point.

I have a DBController that gets invoked when there is a request to the DB.

The DBController's constructor is like this:

public class DBController : Controller {     public DBController()     {         HttpCookie StudentCookies = new HttpCookie("StudentCookies");         StudentCookies.Value = "hallo";         StudentCookies.Expires = DateTime.Now.AddHours(1);         Response.Cookies.Add(StudentCookies);         Response.Flush();     }      [... more code ...]  } 

I get the Error "Object reference not set to an instance of an object" at:

StudentCookies.Expire = DateTime.Now.AddHours(1); 

This is a kind of a basic error message. So what kind of basic thing I've forgot?

Answer 1

The problem is you cannot add to the response in constructor of the controller. The Response object has not been created, so it is getting a null reference, try adding a method for adding the cookie and calling it in the action method. Like so:

private HttpCookie CreateStudentCookie() {     HttpCookie StudentCookies = new HttpCookie("StudentCookies");     StudentCookies.Value = "hallo";     StudentCookies.Expires = DateTime.Now.AddHours(1);     return StudentCookies; }  //some action method Response.Cookies.Add(CreateStudentCookie());