Partial mapping in Entity Framework 4

Question

I want to be able to do the following:

I have a model and inside there I do have an entity.

This entity has the following structure:

public class Client
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Description { get; set; }
}

What I want now, is to just get the client name based on the id. Therefore I wrote a stored procedure which is doing this.

CREATE PROCEDURE [Client].[GetBasics]
@Id INT
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;


SELECT 
    Name
FROM Client.Client
INNER JOIN Client.Validity ON ClientId = Client.Id
WHERE
    Client.Id = @Id; 
 END

Now, going back to VS, I do update the model from the database with the stored procedure included.

Next step is to map this stored procedure to the client entity as a function import.

This also works fine.

Trying now to load one client's name results into an error during runtime...

"The data reader is incompatible with the specified 'CSTestModel.Client'. A member of the type, 'Id', does not have a corresponding column in the data reader with the same name."

I am OK with the message. I know how to fix this (returning as result set Id, Name, Description).

My idea behind this question is the following:

I just want to load parts of the entity, not the complete entity itself. I have a restriction here to just use stored procedures for the entire communication towards/from the database.

Is there a solution to my problem (except creating complex types, LINQ on the result set itself)? And if yes, can someone point me to the right direction?

Many thanks,

Dimi

Craig Stuntz · Accepted Answer · 2010-04-20 12:59:41Z

1

Just project onto a POCO:

var q = from c in Context.Clients
        select new NameOnlyPresentation
                   {
                       Id = c.Id,
                       Name = c.Name
                   };

... or just the name:

public string ClientName(int id)
{
    return (from c in Context.Clients
            where c.Id == id
            select c.Name).FirstOrDefault();
}

answered Apr 20, 2010 at 12:59

Craig Stuntz

127k12 gold badges257 silver badges275 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Dimi Takis Over a year ago

well, forgot to mention that I know about this one too :) Will edit my question to be more precise there.

Craig Stuntz Over a year ago

If you know about the really simple solution, what is there about your problem which is driving you to ask for a very difficult solution? Sounds like there's something missing here.

Dimi Takis Over a year ago

The use of stored procedures and getting the benefits of the mapping feature of EF is driving me here

Mr Bell Over a year ago

I see partially populating an object as a useful thing, also. Having to generate a distinct poco for each type of partial population is cumbersome, and seems unnecessary.

Collectives™ on Stack Overflow

Partial mapping in Entity Framework 4

1 Answer 1

4 Comments

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Related