Object reference not set to an instance of an object

Question

Getting this error on this code:

string pname = null; pname = ag.FirstOrDefault().arrangement.parent.name;

when calling the line pname = ag.FirstOrDefault.....

The filed parent.name is empty(null), which is fine I want to get an empty(null) string in such case. How can I get rid of the error?

LukeH · Accepted Answer · 2011-04-28 11:33:31Z

6

Either ag is null, the FirstOrDefault call is returning null, arrangement is null, or parent is null.

Only you are in a position to determine which one of those is actually the culprit.

answered Apr 28, 2011 at 11:33

LukeH

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1 Comment

Euphoric Over a year ago

+1 I would recomend use debuger or divide it into multiple statements.

Security Hound · Accepted Answer · 2011-04-28 11:42:31Z

If the property ag.FirstOrDefault().arrangement.parent.name is null it means the object ag is null also. This is the reason you are getting object reference error.

The answer Leons provided is actually what I was going to suggest. You need to do some research on the problem its one of the simplest thing to avoid ( trying to reference a null object ) in programming.

It doesn't necessarily mean ag is null. ag might be null; the output of FirstOrDefault might be null; the arrangement member might be null; the parent member might be null.

Leons · Accepted Answer · 2011-04-28 11:45:27Z

You cannot access the properties of a null object. If ag.FirstOrDefault() will return null, then you will not be able to access arrangement.

var temp = ag.FirstOrDefault(); string pname = (temp!= null) ? temp.arrangement.parent.name : null;

You may need to do further null checking.

Pranay Rana · Accepted Answer · 2011-04-28 13:28:00Z

try

var obj = ag.FirstOrDefault(); if( obj !=null) pname = obj.arrangement.parent.name ?? String.Empty;

or you can try

//This will set the variable to null: var obj = ag.FirstOrDefault(); if( obj !=null) pname = Convert.ToString(obj.arrangement.parent.name);

Note : ag.FirstOrDefault().arrangement.parent.name is nullable type

This will throw an exception if ag.FirstOrDefault() return null
The filed parent.name is empty(null) -- this line is written by op anyways i am updating my ans

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