Get rid off redirecttoaction() nullreference exception ASP.NET MVC

Question

1.00/5 (2 votes)

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I'm trying to send a string Id from one action in one controller to another action in another controller using RedirectToAction() but i keep getting a null reference exception:

This is the error: Object reference not set to an instance of an object.

RedirectToAction() method i'm using:

C#

return RedirectToAction("Index", "Assignments", new { cid = id.ToString() });

the http request i'm getting:

http:/localhost:13501/Assignments?cid=CAIS132

instead of this:

http:/localhost:13501/Assignments/index/CAIS132 Knowing that this works

Here's the first Action:

C#

//In Courses Controller
public ActionResult ManageCourse(object id)
    {
        if (id == null)
        {
            return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
        }
        return RedirectToAction("Index", "Assignments",new{cid=id.ToString()});
    }

And here's my other action:

C#

//In Assignments Controller
public ActionResult Index(string id)
    {
        //Some Model retrieval from database using the givin Id
        return View(model);
    }

and here's my RouteConfig.cs:

C#

public static void RegisterRoutes(RouteCollection routes)
    {
        routes.IgnoreRoute("{resource}.axd/{*pathInfo}");

        routes.MapRoute(
            name: "Default",
            url: "{controller}/{action}/{id}",
            defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
        );

The id attribute in the Index action is received null! Any ideas?

What I have tried:

I've tried a couple of thing and i cannot seem to find a solution for it!!
Please do anyone have any idea?

and when I use this:

C#

return RedirectToAction("Index", "Assignments", id.ToString());

<I get this url with a NullReference:

http:/localhost:13501/Assignments?Length=7

Posted 24-Apr-17 7:30am

Member 13149120

Updated 24-Apr-17 8:32am

v2

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Comments

[no name] 24-Apr-17 13:32pm

"Check out my question on stackoverflow", no. If you can't be bothered asking a legitimate question here, there is no reason at all to expect people to go to another web site to see what your question is.

Member 13149120 24-Apr-17 13:41pm

You're Right sir.

Member 13149120 24-Apr-17 13:59pm

Any Ideas ?

[no name] 24-Apr-17 14:14pm

Yes. You are getting a null reference exception for exactly the same reason as everyone else that has ever gotten that exception and you fix it the exact same way.

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OriginalGriff · Accepted Answer · 2017-04-24T08:32:00

This is one of the most common problems we get asked, and it's also the one we are least equipped to answer, but you are most equipped to answer yourself.

Let me just explain what the error means: You have tried to use a variable, property, or a method return value but it contains null - which means that there is no instance of a class in the variable.
It's a bit like a pocket: you have a pocket in your shirt, which you use to hold a pen. If you reach into the pocket and find there isn't a pen there, you can't sign your name on a piece of paper - and you will get very funny looks if you try! The empty pocket is giving you a null value (no pen here!) so you can't do anything that you would normally do once you retrieved your pen. Why is it empty? That's the question - it may be that you forgot to pick up your pen when you left the house this morning, or possibly you left the pen in the pocket of yesterdays shirt when you took it off last night.

We can't tell, because we weren't there, and even more importantly, we can't even see your shirt, much less what is in the pocket!

Back to computers, and you have done the same thing, somehow - and we can't see your code, much less run it and find out what contains null when it shouldn't.
But you can - and Visual Studio will help you here. Run your program in the debugger and when it fails, VS will show you the line it found the problem on. You can then start looking at the various parts of it to see what value is null and start looking back through your code to find out why. So put a breakpoint at the beginning of the method containing the error line, and run your program from the start again. This time, VS will stop before the error, and let you examine what is going on by stepping through the code looking at your values.

But we can't do that - we don't have your code, we don't know how to use it if we did have it, we don't have your data. So try it - and see how much information you can find out!