Short-circuiting in Linq-Where

Question

I have a problem in a Linq-Where method. I get a NullReferenceException in a where clause, which should not happen because C# should use short-circuiting and the second operations hould not be executed:

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If Item is null, Item.State == ... should not be called, because the condition is already true (short-circuiting).

But it seems, that short-circuiting does not working in this case.

Does anyone else had and solved this problem? Thank you!

Edit: In the end, the connectionList should not contains any null-values and no broken connections.

I want the nulls, because i want to remove them from the list. — BendEg, Jan 12 '15 at 10:40
@BendEg How about `connectionList = connectionList.Where(x => x != null && x.State != System.Data.ConnectionState.Broken)`? No need for a foreach loop anymore. Also, I realize this doesn't answer your specific problem. — dcastro, Jan 12 '15 at 10:41
I dont get it, you're selecting the nulls into a list only to remove them later - why not just exclude them in the first place?! — Jamiec, Jan 12 '15 at 10:45
Thats a good point, i try to filter at first with: `connectionList.Remove(null);` — BendEg, Jan 12 '15 at 10:48
Please state what you ACTUALLY WANT in the list at the end of all filtering. Everyone is just guessing your intent. — Jamiec, Jan 12 '15 at 10:48
Perhaps `Item` is not null, but `Item.State` still throws an exception. — CodesInChaos, Jan 12 '15 at 10:49
Never seen so many down votes on answers after watching a question for just 5 minutes. — Segers-Ian, Jan 12 '15 at 10:49
@Selman22 Made a good point in my answer. If || short circuits if the first condition is true, which I thought was the case that code should not have thrown. So what the frak? http://uk.mathworks.com/help/matlab/ref/logicaloperatorsshortcircuit.html — Lews Therin, Jan 12 '15 at 10:52
its because you have a `ToList()` after the `Where` selection. — Vignesh.N, Jan 12 '15 at 10:58

score 0 · Answer 1 · edited May 23 '17 at 11:53

This is common problem, when querying against databases. Namely, translating short-circuiting behavior against databases, don't work the way as you would expect. You can read more about such behavior: The || (or) Operator in Linq with C#

You could try this:

connectionList.RemoveRange(connectionList.Where(x => x==null));
connectionList.SaveChanges();
connectionList.RemoveRange(connectionList.Where(x => x.Item==BrokenState));

just to see if it works.

Short-circuiting in Linq-Where

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