Select from multiple tables using Entity Framework

Question

I am using Entity Framework. I want to select data from multiple tables in the database having no foreign key relation like

select  
    tOut.columnId, wo.columnType, tIn.* 
from 
    TbaleA tIn,
    TableB tOut,
    TableC wo
where
    1 = 1
    and tIn.columnRefId = tOut.columnGuid
    and tOut.columnId = wo.columnId

Is there any solution in Entity Framework for this? I have tried by using include syntax its not working for me ..

Answer 1

You can join tables even though no foreign key relation exists if you use the query syntax. It would go something along these lines:

var result = from tIn in yourDbContext.TableA
             join tOut in yourDbContext.TableB on tIn.columnRefId equals tOut.columnGuid
             join wo in yourDbContext.TableC on tOut.columnId equals wo.columnId
             select new { tOut.columnId, wo.columnType, TableA = tIn };

Answer 2

There are examples for both lambda and query syntax on these links:

MSDN 101 LINQ Samples (mostly query syntax)

Nilzor's LINQ 101 Samples - Lambda Style

Answer 3

Another solution is to use/add navigation properties to your classes, as for example:

class TableA {
    Int32 Id {get; set;}

    //navigation property
    TableB b {get; set;}
}

and use them in the query

from a in yourDbContext.TableA
select new { a.Id, a.b.columnType}

Of course there may be a little configuration (code or annotation) to setup the relations to make them fit the database schema. But you will do this effort once and not for every query.