linq to sql using foreign keys returning iqueryable(of myEntity]

Posted by Gern Blandston on Stack Overflow See other posts from Stack Overflow or by Gern Blandston
Published on 2010-05-04T19:56:13Z Indexed on 2010/05/11 4:34 UTC
Read the original article Hit count: 286

Filed under:

LINQ

|

linq-to-sql

|

foreign-keys

I'm trying to use Linq to SQL to return an IQueryable(of Project) when using foreign key relationships. Using the below schema, I want to be able to pass in a UserId and get all the projects created for the company the user is associated with.

DB tables:

Projects
  Projid
  ProjCreator FK (UserId from UserInfo table)
  Companyid FK (CompanyID from Companies table)

UserInfo
  UserID PK
  Companyid FK

Companies
 CompanyId PK
 Description

I can get the iqueryable(of project) when simply getting the ProjectCreator with this:

Return (From p In db.Projects _
 Where p.ProjectCreator = Me.UserId)

But I'm having trouble getting the syntax to get a iqueryable(of projects) when using foreign keys. Below gives me an IQueryable(of anonymous) but I can't seem to convince it to give me an IQueryable(of project) even if I try to cast it:

  Dim retval = (From p In db.Projects _
    Join c In db.Companies On p.CompanyId Equals c.CompanyId _
     Join u In db.UserInfos On u.CompanyId Equals c.CompanyId _
      Where u.Login = UserId)

© Stack Overflow or respective owner

Related posts about LINQ

LINQ to SQL, LINQ to XML and Accessing DataTable using LINQ

as seen on C# Corner - Search for 'C# Corner'
This article demonstrates how to use LINQ on DataTable, XML Data using LINQ to XML and SQL server data base using LINQ to SQL Classes. >>> More
Exception with Linq2SQL Query

as seen on Stack Overflow - Search for 'Stack Overflow'
I am running a query using Linq2SQL that comes down to following query: DateTime? expiration = GetExpirationDate(); IQueryable<Persons> persons = GetPersons(); IQueryable<Items> subquery = from i in db.Items where i.ExpirationDate >= expiration … >>> More
What is Linq?

as seen on ASP.net Weblogs - Search for 'ASP.net Weblogs'
The way data can be retrieved in .NET. LINQ provides a uniform way to retrieve data from any object that implements the IEnumerable<T> interface. With LINQ, arrays, collections, relational data, and XML are all potential data sources. Why LINQ?With LINQ, you can use the same syntax to retrieve… >>> More
Mixing Silverlight-Specific System.Xml.Linq dll with Non-Silverlight System.Xml.Linq dll

as seen on Stack Overflow - Search for 'Stack Overflow'
I have a Logic layer that references Silverlight's System.Xml.Linq dll and a GUI that is in WPF (hence using the non-Silverlight System.Xml.Linq dll). When I attempt to pass an XElement from GUI project to a method in the Logic project, I am getting (basically) "XElement is not of type XElement" errors… >>> More
Subsonic 3 LINQ vs LINQ to SQL

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, I am using SQL Server 2005 in a project. I have to decide about datalayer. I would like to use LINQ in my project. I saw SubSonic 3 supporting LINQ and I also have option for LINQ to SQL, because i can have typed lists from LINQ to SQL. I am wondering what is different between LINQ to SQL and… >>> More

Related posts about linq-to-sql

how can i page my linq to sql result set

as seen on Stack Overflow - Search for 'Stack Overflow'
Remembering MySQL could use the instruction "limit" to indicate where I was starting my result set and how many wanted to have included. Select * FROM Users Limit [start], [Length] How can I do this in LinqToSql >>> More
LINQ to SQL and missing Many to Many EntityRefs

as seen on West-Wind - Search for 'West-Wind'
Ran into an odd behavior today with a many to many mapping of one of my tables in LINQ to SQL. Many to many mappings aren’t transparent in LINQ to SQL and it maps the link table the same way the SQL schema has it when creating one. In other words LINQ to SQL isn’t smart about many to many mappings… >>> More
Comparing LINQ to SQL vs the classic SqlCommand

as seen on Dot net Slackers - Search for 'Dot net Slackers'
tweetmeme_url = 'http://alpascual.com/blog/comparing-linq-to-sql-vs-the-classic-sqlcommand/';tweetmeme_source = 'alpascual';When you are coming from using SqlCommand and SqlConnection is difficult to move to another library for your database needs. For those people still in the limbo to make the decision… >>> More
Comparing LINQ to SQL vs the classic SqlCommand

as seen on Dot net Slackers - Search for 'Dot net Slackers'
tweetmeme_url = 'http://alpascual.com/blog/comparing-linq-to-sql-vs-the-classic-sqlcommand/';tweetmeme_source = 'alpascual';When you are coming from using SqlCommand and SqlConnection is difficult to move to another library for your database needs. For those people still in the limbo to make the decision… >>> More
LINQ to SQL Profiler

as seen on Dot net Slackers - Search for 'Dot net Slackers'
In this article we will be taking a look at the new LINQ to SQL Profiler from HibernatingRhinos. This tool gives you a view into the goings on of LINQ to SQL. Not only does it allow you to see the SQL that is generated by your LINQ queries but it also shows you information about your connections… >>> More