Null reference exception when using Find on custom object

Question

I'm scratching my head a bit here.

I have a custom object which I'm trying to search for a property that starts with some text.

If I search for a property using == instead of StartsWith it doesn't error.

This works

Server serverObject = ServerObjectList.Find(n => n.Name == "Server001");

This gives a null ref exception

Server serverObject = ServerObjectList.Find(n => n.Name.StartsWith("Server001"));

Oddly, it works if the first object is the one your looking for.

Rakesh · Answer 1 · 2015-07-19T15:00:23.950

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your "ServerObjectList" list might be empty. At first it might be evaluating null == "" which gives false. in second statement, you are calling StartsWith function on a null, which gives you nullrefrenceexception. check if the list already has data.

Note: == operator is overloaded for strings. This might be doing null check before returning false.

edited Jul 19 '15 at 15:00

answered Jul 19 '15 at 14:53

Rakesh

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Yeah I already checked and my ServerObjectList is full of objects. – RickBowden Jul 19 '15 at 15:04
ok, does every object has Name property not null? – Rakesh Jul 19 '15 at 15:07
Yep, all objects in he list have a name property. Non are null or empty. – RickBowden Jul 19 '15 at 15:26
Ah, I just found a server with no name. Didn't see it at first. – RickBowden Jul 19 '15 at 15:38
Yes, you can update your code to check nulls. – Rakesh Jul 19 '15 at 16:09

score 0 · Accepted Answer · edited Jul 19 '15 at 15:43

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You should be doing like this as n may be null or Name may be null:

Server serverObject = ServerObjectList.Find(n => n!=null && n.Name!=null && n.Name.StartsWith("Server001"));

edited Jul 19 '15 at 15:43

marc_s

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answered Jul 19 '15 at 15:27

Deepak Bhatia

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Thanks Deepak. That gets around the null server name I hadn't spotted. – RickBowden Jul 19 '15 at 15:47
Welcome. I am glad that helped. – Deepak Bhatia Jul 19 '15 at 15:49

Null reference exception when using Find on custom object

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