Difference between LINQ Lambda and SQL statement

Question

I have the following lambda statement:

var resources = Db.Resource.Where(w => w.ResValue.Any(a => a.ApplicationFk == applicationPk) && w.CategoryFk == (categoryId ?? w.CategoryFk ) && w.IsEditable);
if (cultureIdsMissing!= null)
{
     resources = resources.Where(w => w.ResValue.Any(a => cultureIdsMissing.Any(aa => aa == a.CultureFk) && a.Value == string.Empty));
 }

This is not returning the result which I want, which is returned by:

SELECT Resource.ResourcePk, Resource.CategoryFk, Resource.Name, Resource.IsEditable, ResValue.ApplicatieFk, ResValue.CultureFk, ResValue.Value
FROM Resource 
INNER JOIN ResValue ON Resource.ResourcePk = ResValue.ResourceFk
WHERE (ResValue.ApplicatieFk = 6) 
AND (Resource.IsEditable = 1) 
AND (ResValue.Value = '') 
AND (ResValue.CultureFk = 1 OR ResValue.CultureFk = 2)

Not that cultureIdsMissing is a List containing both the numbers 1 and 2. What am I missing or doing wrong with the lambda query?

Answer 1

I think you have to remove && w.CategoryFk == (categoryId ?? w.CategoryFk ) from your linq lemda expression. if categoryId = 1 then it will take only records with value 1 . So try after remove that. Your linq code should be this.

var resources = Db.Resource.Where(w => w.ResValue.Any(a => a.ApplicationFk == applicationPk)&& w.IsEditable);
if (cultureIdsMissing!= null)
{
    resources = resources.Where(w => w.ResValue.Any(a => cultureIdsMissing.Any(aa => aa == a.CultureFk) && a.Value == string.Empty));
}

Answer 2

You should take it from your sql statement :

Db.Resource
.Join(Db.ResValue
, rs => rs.ResourcePk
, resV => resv.resourceFk
, (rs, resv) => new { res = rs, resV = resV })
.Where(w => w.resv.ApplicatieFk == 6
&& w.res ==1
&& resv.Value == string.empty()
&& (resv.CultureFk == 1 || resv.CultureFk == 2))

It's not tested so maybe it won't work on first try.

Answer 3

I would translate the SQL to query comprehension syntax. In general, convert phrases in query comprehension order, use table aliases as range variables (or create range variables), and put unary/overall aggregate functions (such as TOP , DISTINCT or SUM ) as function calls outside the whole query. For your SQL,

var ans = from r in Resource
          where r.IsEditable == 1
          join rv in ResValue on r.ResourcePk equals rv.ResourceFk
          where rv.ApplicatieFk == 6 && rv.Value == "" && (rv.CultureFk == 1 || rv.CultureFk == 2)
          select new { r.ResourcePk, r.CategoryFk, r.Name, r.IsEditable, rv.ApplicatieFk, rv.CultureFk, rv.Value };