Conditional operator for more than 1 values checking in C#

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Could you please help me that how to check more than 1 values to check in c# lamda expression

DocumentationLink = context.APIDocumentationTypes.Where(x => x.DocumentationTypeId == a.DocumentationTypeId).Select(x => x.DocumentationDescription).FirstOrDefault().ToLower() != "value1" ? a.DocumentationLink : "",

i need to check with

value1

and

value2

in same line.

What I have tried:

<pre>DocumentationLink = context.APIDocumentationTypes.Where(x => x.DocumentationTypeId == a.DocumentationTypeId).Select(x => x.DocumentationDescription).FirstOrDefault().ToLower() != "value1" && "value2"? a.DocumentationLink : "",

Posted 14-Aug-17 1:43am

DGKumar

Updated 14-Aug-17 3:09am

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OriginalGriff · Answer 1 · 2017-08-14T02:25:00

Solution 1

Try:

C#

string result = context.APIDocumentationTypes.Where(x => x.DocumentationTypeId == a.DocumentationTypeId)
                                             .Select(x => x.DocumentationDescription)
                                             .FirstOrDefault().ToLower();
DocumentAtionLink = ( result != "value1" && result != "value2") ? a.DocumentationLink : "";

But do note that FirstOrDefault will return null if there are no elements that matched your Select - at which point your ToLower call will cause a NullReferenceException.

Posted 14-Aug-17 2:25am

OriginalGriff

Updated 14-Aug-17 2:26am

v2

Comments

BillWoodruff 14-Aug-17 9:56am

Hi, I keep seeing that call to'FirstOrDefault without a predicate followed by 'ToLower as a guaranteed error. I miss something ?

OriginalGriff 14-Aug-17 10:27am

FirstOrDefualt doesn't need a predicate / lambda expression - it just returns the first of a enumerable sequence, or null if the collection is empty.
Since the Select that precedes it returns an IEnumerable string collection (or it couldn't be compared in his original code with a string) you can call ToLower on it.
Me, I'd omit the ToLower until after I'd checked the null return, but your solution of using it inside the Select lambda is just as efficient (as the whole sequence isn't evaluated with a FirstOrDefault, so it doesn't generate unwanted strings for each element).

[edit]FirstOrDefualt can take a lambda. of course.[/edit]

OriginalGriff 14-Aug-17 10:29am

:doh: Brain death is setting in - FirstOrDefault *can* accept a predicate, of course it can. :sigh:

BillWoodruff 14-Aug-17 12:25pm

My brain damage is greater than your brain damage, and, I've got years of mileage on my neurons to prove it :)

My impression is that the OP wants to iterate the matches for x.DocumentationTypeId == a.DocumentationTypeId).Select(x => x.DocumentationDescription and then find the first one in that IEnumerable<ocumentationdescription> that doesn't match on "value1" and "value2"

BillWoodruff · Answer 2 · 2017-08-14T03:09:00

Here's a guess at what you might need to do:

private DocumentationLink getadl(AContext ctx, APIDocumentationTypes a)
{
    var adl = ctx.APIDocumentationTypes.Where(x => x.DocumentationTypeId == a.DocumentationTypeId)

        .Select(x => x.DocumentationDescription.ToLower())

        .FirstOrDefault(
            descr => !(descr == "value1" || descr == "value2")
    );

    // what is the default Type here if no match is found ?
    return (adl == "") ? null : a.DocumentationLink;
}

Of course, you can create "intermediate" variables in a 'Select query, if necessary/