Question

I am trying to create a ViewModel for data that I want to display in my view. The issue is, the data being displayed is spread across 2 databases and multiple tables within each. I’ve read that you cannot join Linq queries across multiple contexts, which makes sense, and I’ve also read that we can’t use Code-First in EF5 to use Stored Procedures….which led me to using 3 different Linq queries and attempt to combine them into 1 ViewModel…I’m just not sure how to get there.

Here’s my Linq queries:

var csdContext = new CSDContext(CustomerCode);
var masterContext = new MasterContext();

//Only returns 1 row - which is what we want.
List<Site> sites = (from s in csdContext.Sites
                join sa in csdContext.SiteAddresses
                    on s.SiteID equals sa.SiteID
                join a in csdContext.Addresses
                    on sa.AddressID equals a.AddressID
                join spv in csdContext.SiteProductVersions
                    on s.SiteID equals spv.ProductVersionID
                where s.SiteID == id
                select s).ToList();

//List
List<States> states = (from s in masterContext.StatesTable
                    select s).ToList();

My ViewModel looks like this:

public class SiteDetailsViewModel
{
    public string Address { get; set; }
    public string Address2 { get; set; }
    public string City { get; set; }
    public string StateCode { get; set; }
    public string ZipCode { get; set; }
    public string OfficePhone { get; set; }
    public string MobilePhone { get; set; }
    public string AlternativePhone { get; set; }
    public int ProductVersionID { get; set; }
}

Basically, I need the following data from these tables:
csdContext – Address
Address
Address2
City
ZipCode

csdContext – Sites
OfficePhone
MobilePhone
AlternativePhone

csdContext – SiteProductVersions
ProductVersionID

masterContext – States
StateCode

Here’s how the tables are joined in SQL:

SELECT csd_a.Address, csd_a.Address2, csd_a.City, mstr_st.StateCode, csd_a.ZipCode, csd_s.OfficePhone, csd_s.MobilePhone, 
csd_s.AlternativePhone, csd_spv.ProductVersionID
FROM CSD.dbo.Sites AS csd_s 
INNER JOIN  CSD.dbo.SiteAddress AS csd_sa ON csd_sa.SiteID = csd_s.SiteID 
INNER JOIN  CSD.dbo.Address AS csd_a ON csd_a.AddressID = csd_sa.AddressID 
INNER JOIN CSD.dbo.SiteProductVersions AS csd_spv ON csd_s.SiteID = csd_spv.SiteID 
INNER JOIN MasterDB.dbo.States AS mstr_st ON mstr_st.StateID = csd_a.StateID 

I can’t figure out how to merge these 3 results to create the ViewModel data for SiteDetailsViewModel. Can anyone help?

Answer 1

If you materialize your queries as described in OP you can use this:

var query = sites.Join(
            states,
            si => si.StateID,
            st => st.StateID,
           (si, st) => new SiteDetailsViewModel
                        {
                             Address = si.Address,
                             Address2 = si.Address2,
                             City = si.City,
                             StateCode = st.StateCode,
                             ZipCode = si.ZipCode,
                             OfficePhone = si.OfficePhone,
                             MobilePhone = si.MobilePhone,
                             AlternativePhone = si.AlternativePhone,
                             ProductVersionID = siProductVersionID
                        });