CODEWITHSUNDEEP
c#linq
Cameron Castillo
Cameron Castillo

Reputation: 2832

Linq to SQL check for null strangeness

I have a Linq to SQL query that behaves (in my opinion) very strange when I check for null values.

There is a record in the DB as shown by the last Linq, but why does the 1st two queries not show the record?

//Check
(record.SomeID == null ? "Yes" : "No"); //This prints Yes

//LINQ
var q = (from t in mySQLTable
         where t.PKID == record.PKID && 
         t.SomeID == record.SomeID
         select t).FirstOrDefault();
 //This prints nothing.  I.e. no records found

var q2 = (from t in mySQLTable
          where t.PKID == record.PKID &&
          t.SomeID == (record.SomeID == null ? null : record.SomeID)
          select t).FirstOrDefault();
 //This also prints nothing.  I.e. no records found

 var q3 = (from t in mySQLTable
           where t.PKID == record.PKID &&
           t.SomeID == null
           select t).FirstOrDefault();
 //This prints 1 record

Upvotes: 0

Views: 66

Answers (1)

Zein Makki
Zein Makki

Reputation: 30022

You can overcome this issue using the below query:

bool isNull = record.SomeID == null;

var q = (from t in mySQLTable
         where t.PKID == record.PKID 
         && ( (isNull && t.SomeID == null)
             ||
              (!isNull && t.SomeID == record.SomeID)
            )
         select t).FirstOrDefault();

Upvotes: 1

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