LINQ查询C＃错误的结果

Question

I write this query but the result from it is wrong

var query = from item in db.Advances
            where CurrentConfiguration.currentLanguage == GeneralDefinitions.arabicSymbol 
                  ? item.eUser.name.ToLower().Contains(strSearchKey)
                  : item.eUser.englishName.ToLower().Contains(strSearchKey)
            && !item.isPaid 
            && item.expectedPaymentMonth == dExpectedPayment.Month 
            && item.expectedPaymentYear == dExpectedPayment.Year
            && item.advanceTypeId == (int)enumAdvanceType.AtOnce
            select item;

The wrong is in

item.expectedPaymentMonth == dExpectedPayment.Month 
&& item.expectedPaymentYear == dExpectedPayment.Year

It is always true although item.expectedPaymentMonth != dExpectedPayment.Month Is there any syntax error or something wrong in this query ?

Answer 1

You must group boolean s because of ?: expression! See:

var query = from item in db.Advances
            where 
            (
                CurrentConfiguration.currentLanguage == GeneralDefinitions.arabicSymbol 
                ? item.eUser.name.ToLower().Contains(strSearchKey)
                : item.eUser.englishName.ToLower().Contains(strSearchKey)
            )
            && !item.isPaid 
            && item.expectedPaymentMonth == dExpectedPayment.Month 
            && item.expectedPaymentYear == dExpectedPayment.Year
            && item.advanceTypeId == (int)enumAdvanceType.AtOnce
            select item;

If you don't use () , all expressions after item.eUser.englishName.ToLower().Contains(strSearchKey) will be AND with item.eUser.englishName.ToLower().Contains(strSearchKey) and finally returns a single result! ALSO you can use separate where clauses:

var query = from item in db.Advances
            where 
                CurrentConfiguration.currentLanguage == GeneralDefinitions.arabicSymbol 
                ? item.eUser.name.ToLower().Contains(strSearchKey)
                : item.eUser.englishName.ToLower().Contains(strSearchKey)
            where !item.isPaid 
                && item.expectedPaymentMonth == dExpectedPayment.Month 
                && item.expectedPaymentYear == dExpectedPayment.Year
                && item.advanceTypeId == (int)enumAdvanceType.AtOnce
            select item;

Answer 2

Try this:

var query =
    from item in db.Advances
    where (CurrentConfiguration.currentLanguage
            == GeneralDefinitions.arabicSymbol
            ? item.eUser.name
            : item.eUser.englishName).ToLower().Contains(strSearchKey)
    where !item.isPaid
    where item.expectedPaymentMonth == dExpectedPayment.Month
    where item.expectedPaymentYear == dExpectedPayment.Year
    where item.advanceTypeId == (int)enumAdvanceType.AtOnce
    select item;

I suspect that the ternary operator is causing you grief.

Answer 3

Perhaps because the ? operator is not between () and you are testing arabicSymbol ?

try: (extra lines added for clarity)

where

(

CurrentConfiguration.currentLanguage == GeneralDefinitions.arabicSymbol ? item.eUser.name.ToLower  ().Contains(strSearchKey) : item.eUser.englishName.ToLower().Contains(strSearchKey) 

)
                    && !item.isPaid && item.expectedPaymentMonth == dExpectedPayment.Month && item.expectedPaymentYear == dExpectedPayment.Year 
                    && item.advanceTypeId == (int)enumAdvanceType.AtOnce 
                    select item; 

Answer 4

Both answers above are correct as they relate to operator prescedence (http://msdn.microsoft.com/en-us/library/aa691323(v=vs.71).aspx)

The && is evaluated before the ?:. Therefore you're effectively seeing all the &&'s being applied the the else portion of the ?: expression.