Possible NullreferenceException

Question

Resharper is showing a "Possible System.NullReferenceException" warning. I however can't see how I can get one.

public class PlaceController : PlanningControllerBase
{
    [Authorize]
    public ActionResult StartStop(int id)
    {
        if (Request != null && Request.Cookies != null && Request.Cookies["place"] != null)
        {
            if (Request.Cookies["place"].Value != null)//Possible NullReferenceException?
            {
                string placeInformation = Request.Cookies["place"].Value;//Possible NullReferenceException?
                //...
            }
        }
    }
}

How can this give a NullReference if I check all fields? Using the following doesn't show the warning:

Request.Cookies[0];//Index instead of name

Edit: updated code.

Is there a reason why you want to set the variable `placeInformation` when `Request.Cookies["place"].Value` is null or was that a mistake? — Çağdaş Tekin, Mar 04 '10 at 15:35

score 7 · Accepted Answer · answered Mar 04 '10 at 15:33

I assume the checker isn't checking the value of the string passed to the CookieCollection indexer is the same each time. I imagine if you restructure the code to:

if (Request != null && Request.Cookies != null) 
{
    var place = Request.Cookies["place"];
    if (place != null && place.Value == null) 
    { 
        string placeInformation = place.Value;
    } 
}

It might work.

score 4 · Answer 2 · answered Mar 04 '10 at 15:47

4

You don't need to listen to every single warning. The Request object and the Cookies object will never be null so this is all you need.

var placeCookie = Request.Cookies["place"]; 
if (placeCookie != null)
{
    string placeInformation = placeCookie.Value;
}

answered Mar 04 '10 at 15:47

ChaosPandion

77,506
18
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Indeed, just writing "HttpCookie cookie = Request.Cookies["place"];" works and shows no warnings. – Carra Mar 04 '10 at 15:54
@Carra - Just a side note, I think using indeed in your day to day vocabulary is indeed awesome. – ChaosPandion Mar 04 '10 at 15:57
English isn't my native language. I meant to use "Yes,...". – Carra Mar 04 '10 at 16:03
@Cara - I was not implying that you English was incorrect. I was simply saying that I like the word indeed from some strange reason. – ChaosPandion Mar 04 '10 at 16:18

score 0 · Answer 3 · answered Mar 04 '10 at 15:36

0

err don't you want Request.Cookies["place"].Value != null , right now you will only be setting placeInformation to null.

answered Mar 04 '10 at 15:36

Hogan

69,564
10
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Possible NullreferenceException

3 Answers3