Using a conditional if statement in a Linq query

Question

I'm trying to write a linq query that uses an if statement.

In the code below I'm searching for matches of

n.SAU_ID = sau.SAUID where

ReportingPeriod column contains "Oct1" then FiscalYear - aprYearDiff = sau.SAUYearCode.

Else

FiscalYear - octYearDiff = sau.SAUYearCode.

My code is only giving matches for the SAUID and "Oct1".

What code is needed to implement theese statements?

    int FiscalYear = 2014;       

    List<String> addtowns = new List<string>();

    List<Stage_Reorg> reorg = _entities.Stage_Reorg.ToList();

    int aprYearDiff = 2;
    int octYearDiff = 1;

    foreach (var sau in reorg)
    {
        addtowns.AddRange(_entities.Stage_EPSSubsidySADCSDTown
        .Where(n => n.SAU_ID == sau.SAUID 
            && (n.ReportingPeriod == "Oct1" 
            ? (FiscalYear - aprYearDiff) == sau.SAUYearCode 
            : (FiscalYear - octYearDiff) == sau.SAUYearCode))
        .Select(n =>  n.TownCode ));
    }

you can fix the syntax but I don't think it will work with EF anyway. — Selman Genç
– Selman Genç, Commented Aug 29, 2014 at 18:24
.where( a => { /*some code */ return /*some bool value*/} ) — RadioSpace
– RadioSpace, Commented Aug 29, 2014 at 18:26
@EugenePodskal That was actually easier to read before the edit. — DCShannon
– DCShannon, Commented Aug 29, 2014 at 18:32
@DCShannon Well, I do not say that I've made some really good formatting there. Just I am a firm believer in fair use of tabs and abundant use of parentheses to make code more readable (at least for me). Overall it is a matter of taste and personal preferences, so feel free to rollback it. — Eugene Podskal
– Eugene Podskal, Commented Aug 29, 2014 at 19:04

Stilgar · Accepted Answer · 2014-08-29 18:28:00Z

1

This is a bad idea anyway. Transform the condition to

(n.ReportingPeriod == "Oct1" && (FiscalYear - aprYearDiff) == sau.SAUYearCode)  
|| (n.ReportingPeriod != "Oct1" && (FiscalYear - octYearDiff) == sau.SAUYearCode)

answered Aug 29, 2014 at 18:28

Stilgar

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2 Comments

DCShannon Over a year ago

Could elaborate on why it's a bad idea, but upvoted anyway, as this should work better and is logically equivalent.

Stilgar Over a year ago

Because declarative code is better than imperative code and this one is simpler.

Selman Genç · Accepted Answer · 2014-08-29 18:25:50Z

1

Here is a possible way but this probably won't work with EF. You will need to load all records into memory then perform the filtering:

addtowns.AddRange(_entities.Stage_EPSSubsidySADCSDTown
    .Where(n => { 
                   bool b = n.ReportingPeriod == "Oct1" 
                           ? (FiscalYear - aprYearDiff) == sau.SAUYearCode 
                           : (FiscalYear - octYearDiff) == sau.SAUYearCode);
                  return b && n.SAU_ID == sau.SAUID;
                 }).Select(n =>  n.TownCode ))

answered Aug 29, 2014 at 18:25

Selman Genç

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1 Comment

RadioSpace Over a year ago

I take to long to type. but I agree completely

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