Filter data using LINQ from two tables!

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LINQ

I have two table :

Table 1 : Items

ItemsId  Name_En   
   1      Cream
   2      Oil
   3      Detergent
   4      Soap

Table 2 : ItemsCommon

ItemsCommonId  ItemsId    Name_En         CategoryId
  1                1        Face Cream          3
  2                2        Head Oil            3
  3                1        Foot Cream          4
  4                2        Body Oil            4

Now what I want if user search items by categoryid = 3 then it will show result like :

ItemsId   Name_En   
   1      Face Cream
   2      Head Oil
   3      Detergent
   4      Soap

or search items by categoryid = 4 then result will be :

ItemsId   Name_En
   1      Foot Cream
   2      Body Oil
   3      Detergent
   4      Soap

but if user search by other categoryid except 3, 4 then result will be same as Items table :

ItemsId  Name_En   
   1      Cream
   2      Oil
   3      Detergent
   4      Soap

I try this method..

public List<Items> SearchItemsByCategory(int categoryid )
      {
          var items= (from i in db.Items
                      join ic in db.ItemsCommon on i.ItemsId equals ic.ItemsCommonId
                      into tempJoin
                      from t2 in tempJoin.DefaultIfEmpty()
                      select new { t2.Id,t2.Name,t2.ItemsId,t2.CategoryId }).ToList();
          return items;

         // var result = casePartyRoles.Where(c=>c.)
      }

Any suggestion really appreaciated !