Entity Framework Query - how to return desired results

Question

I have this query

ViewBag.Tags = db.Tag_Group
   .Where(u => 
      u.Tags.Any(d => d.CategoryName.Contains("|" + CategoryID + "|")) 
      & u.Tags.Any(s=>s.Tag_List.Any(d=>d.Item.ItemsOnStock>0)))
   .OrderBy(y => y.TagGrupName)
   .ToList();

It returns all groups and not only ItemsOnStock>0 groups.

What am I doing wrong ?

Tag_List has many Item and many Tags . Tag_Group has many Tags

Table Tag_List is used to store Tags for specific Items .

I only need List<Tag_Group> for items that are on stock. Is there some better way to do this ?

Answer 1

This is a disguised "filtered Include" question and the answer is similar to the usual work-around for lack of filtering in Include .

In your case, you better start the query at the Tags and group them by their TagGroup (of which I assume the navigation property exists):

db.Tags
  .Where(t => t.CategoryName.Contains("|" + CategoryID + "|") 
           && t.Tag_List.Any(d => d.Item.ItemsOnStock > 0))
  .GroupBy(t => t.TagGroup)
  .AsEnumerable()
  .Select(g => g.Key)
  .OrderBy(y => y.TagGroupName)
  .ToList();

Remember to disable lazy loading, so the groups' Tags collections won't be populated fully when you access them.

Answer 2

Could it be that you get the wrong result because of your one & instead of && ?

So you have a class Tag_Group . Every object of Tag_Group has zero or more Tags .

Every Tag has a string CategoryName and an IEnumerable Tag_List that contains zero or more Items . Every Item has an int(?) property ItemOnStock . The int part is not important. It can be any class as long as you can compare it with zero.

It seems you want all Tag_Group objects that have at least one Tag in its sequence of Tags that:

• Has a CategoryName equal to "|" + CategoryID + "|"
• AND has at least one item in Tag_List that has an ItemOnStock > 0

Or could it be that you want all Tag_Group objects that

• Has at least one Tag in Tags with a CategoryName equal to "|" + CategoryID + "|"
• OR has at least one Tag in Tags that has at leas one item in Tag_List that has an ItemOnStock > 0 . This Tag may be a different Tag than the one with the CategoryName

I assume you want the AND option.

Although you didn't say so, I assume db is your dbContext, and you want your query to be performed by the database, so AsQueryable, and not AsEnumerable.

var CategoryId = ...
string categoryName = "|" + CategoryId + "|";

var result = db.Tag_Group
   // I want only those tagGroupElements that have at least one Tag
   // in sequence Tags that matches both conditions:
   .Where(tagGroupElement => tagGroupEleent.Tags
             // the tagGroupElement should have a matching CategoryName
       .Where(tag => tag.CategoryName == categoryName)
             // and the tagGroupElement should have at least one item
             // in Tag_List with ItemOnStock > 0
          && tag.Tag_List
              .Where(tagListElement => tagListElement.ItemOnStock > 0)
              .Any())
       .Any());

Answer 3

Thank you both for your help :)

I ended up using a bit modified Gert's answer since I needed Tags grouped by TagGroup

db.Tags
  .Where(t => t.CategoryName.Contains("|" + CategoryID + "|") 
           && t.Tag_List.Any(d => d.Item.ItemsOnStock > 0))
  .GroupBy(t => t.TagGroup.GroupName)
  .OrderBy(y => y.Key)
  .ToList();

I learned a lot from your answers