NullReference Exception in C#

Question

I'm getting System.NullReferenceException: Object reference not set to an instance of an object. Exception with below code.

   string avblCount = "0";

    if (!string.IsNullOrWhiteSpace(item.PART_AVAILABILITY.AVAIL_COUNT.ToString() as string))
    {
         avblCount = item.PART_AVAILABILITY.AVAIL_COUNT.ToString();
    }

Exception occurred from this line.

if (!string.IsNullOrWhiteSpace(item.PART_AVAILABILITY.AVAIL_COUNT.ToString() as string))

How can i fix this ?

item.PART_AVAILABILITY.AVAIL_COUNT.ToString() as string) why ? do only as string it won't throw error — Kamil Budziewski, Jul 05 '13 at 07:39
`item` or `CAPSLOCKHAPPYPROPERTY` is null, edit, why not just check if these are null instead of converting it to a string first? — Sayse, Jul 05 '13 at 07:39
does every part of item.PART_AVAILABILITY.AVAIL_COUNT exist? What if for example PART_AVAILABILITY is null? — Paul Zahra, Jul 05 '13 at 07:39
_"How can i fix this?"_ - by searching the web. There's thousands of questions on this error on SO alone. Try to understand what the error means. — CodeCaster, Jul 05 '13 at 07:40
If you program in C# you absolutely positively must learn what a NullReferenceException is, how they come about, how they present themselves at runtime, how you can handle them, mitigate them and finally avoid them. — flq, Jul 05 '13 at 07:46

score 3 · Accepted Answer · answered Jul 05 '13 at 07:40

3

One or more of these entities are null:

item
item.PART_AVAILABILITY
item.PART_AVAILABILITY.AVAIL_COUNT

You should check which one is, and then act accordingly

answered Jul 05 '13 at 07:40

LittleSweetSeas

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Are you serious? If item is null, then the 3 are nulls. If item is not null but PART_AVAILABILTY is, then there are 2 nulls. If item and PART_AVAILABILTY aren't null, then AVAIL_COUNT is. – LittleSweetSeas Jul 05 '13 at 07:54
Exactly: they lead to a NullReferenceEx as per question. Is it just a flame or a dictionary-check? – LittleSweetSeas Jul 05 '13 at 07:56
Well, I won't argue nomore, but in my opinion if item is null, all its properties are "undefined": there is no "undefined" key-word in .NET, and obviously it has no sense to enter into reflection to check if a property is available in a given object. So, i used "null" in a unspecific way, but you're right: undeclared/undefined != null to a compiler eyes :) – LittleSweetSeas Jul 05 '13 at 08:08

NullReference Exception in C#

1 Answers1