Why isn't this short circuit in lambda working?

Question

Why linq is trying to check second expression anyway?

.Where(t =>  String.IsNullOrEmpty(someNullString) || t.SomeProperty >= Convert.ToDecimal(someNullstring))

What is usual workaround?

Update:
It is about LINQ to SQL, of course. It cannot translate to SQL.

I suddenly find the => and >= in this code very confusing. :-) (And I've used both quite often, but never together in the same statement.) — Wim ten Brink, Jul 03 '09 at 14:22
Are you sure it isn't working? I've tested it against a list (LINQ To Objects) and seems to work. — jmservera, Jul 03 '09 at 15:05
Read the question again. Of course it works but it also evaluates the second condition while using || should have prevented this... — Wim ten Brink, Jul 03 '09 at 15:52

score 12 · Accepted Answer · answered Jul 04 '09 at 02:25

Is the .Where being used on a Table<>?

If so, then before any data can be grabbed, it must convert the LINQ to SQL and to do that it must convert the string into a decimal. It's not trying to actually perform the comparisons yet, it's trying to build the constructs necessary to retrieve data.

score -1 · Answer 2 · answered Jul 03 '09 at 15:22

I can't reproduce any problem with the short circuit evaluation...

I think this evaluates to something like:

[CompilerGenerated]
private static bool <MyMethod>b__f(MyObject t)
{
    return (String.IsNullOrEmpty(someNullString) 
                 || t.SomeProperty >= Convert.ToDecimal(someNullstring));
}

short circuit works well here.

I suspect other elements in your Enumerable evaluate the first condition (String.IsNullOrEmpty(someNullString)) to false. Can you confirm this?

Provide a bit more code so that we can analyze this.

score -1 · Answer 3 · answered Jul 04 '09 at 02:32

-1

Do you have a variable t in any scope that may be evaluated?

Did you try with parenthesis like this:

.Where(t =>  (String.IsNullOrEmpty(someNullString) || 
             t.SomeProperty >= Convert.ToDecimal(someNullstring)))

?

answered Jul 04 '09 at 02:32

eKek0

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The => defines the scope of t. – Benjamin Autin Jul 04 '09 at 02:42

score -1 · Answer 4 · edited May 23 '17 at 10:32

-1

There is a workaround on The || (or) Operator in Linq with C# according to which you would do in your case something like:

.Where(t =>  t.SomeProperty >= Convert.ToDecimal(someNullstring ?? "0"))

Of course this might not be the solution you need in your particular case, but at least it gives an idea how to bypass the error.

edited May 23 '17 at 10:32

Community

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answered Nov 28 '12 at 17:52

yoel halb

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Why isn't this short circuit in lambda working?

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