Question

What is wrong with this code ?
I got this exception on the last line:

Unable to create a constant value of
type
‘System.Collections.Generic.IEnumerable`1’.
Only primitive types (‘such as Int32,
String, and Guid’) are supported in
this context.

var query = from colT in dal.TBL_Gharardad 
            select colT;  

if(lstTarafeGharardadIds.Count>0)
    query = from q in query 
            join id in lstTarafeGharardadIds on q.TarafeGharardadId equals id 
            select q;

dgvListeGharardad.DataSource = query.ToList();

The lastTarafeGharardadIds is a List<int>

I also test

dgvListeGharardad.DataSource = query;

Everything works well if if expression equals to false and this code

query = from q in query 
        join id in lstTarafeGharardadIds on q.TarafeGharardadId equals id 
        select q;

doesn’t run. But I can’t understand I got the error on the last line (on this code):

dgvListeGharardad.DataSource = query.ToList();

Answer 1

I think linq can’t join between an in-memory collection (lstTarafeGharardadIds) and a database table (dal.TBL_Gharardad, dal.v_Gharardad…).

Similar problem: Why won't this LINQ join statement work?

This should work:

var query = (from colT in dal.TBL_Gharardad select colT).AsEnumerable();;
if (lstTarafeGharardadIds.Count>0)
    query = from q in query 
            join id in lstTarafeGharardadIds on q.TarafeGharardadId equals id 
            select q;
dgvListeGharardad.DataSource = query.ToList();