LINQ to Entities does not recognize the method Int32 get_Item(Int32)

You need to store your int in a variable, so that EntityFramework isn’t trying to pull the whole array into its scope.

var myInt = myInts[0];

var query = (from d in db.MYTABLE
             where d.RELID.Equals(myInt)
             select d.ID).Distinct();

List<int?> urunidleri = query.ToList();