RIA Services - Silverlight 4.0 - Accessing entities from code

Question

I have strange situation I have simple project to test RIA functionality in Silverlight 4.0.

When I use data source for Domain Service it works great but when I want to access Context from code and execute simple query I returns 0 rows.

//test One with query provided to DataSource
var q = ctx.GetDoctorsWithPatientsAndHospitalQuery();
var result = ctx.Load(q);

//test Two using EntityQuery
EntityQuery<Doctor> query =
    from c in ctx.GetDoctorsWithPatientsAndHospitalQuery()
    select c;
LoadOperation<Doctor> loadOp = this.ctx.Load(query);
var result2 = loadOp.Entities;

//test Three using only entity and Linq
var result3 = ctx.Doctors.ToList();

Strange is also that when I want to add new entity instance from code it works great.

Doctor newDoctor = new Doctor()
{
    FirstName = firstNameTextBoxNew.Text,
    LastName = lastNameTextBoxNew.Text,
    Hospital_Id = tmp,
    Hospital = tmpH
};

ctx.Doctors.Add(newDoctor);
ctx.SubmitChanges();

Can anyone could point me what I have done wrong to execute select from code?

Regards, Daniel Skowroński

Answer 1

Calling "LoadOperation loadOp = this.ctx.Load(query);" from code is an async operation so you are basically checking the result before it completes.

If you want to see the results, you need to provide a callback, to the Load() method, that will execute after the data is loaded.

Data sources for domain services handle async updates, so keep propagating changes as and when load operations complete.

Your "save" works as it does not wait around for the result. You are manually checking the database afterwards. Not checking it in code.

Hope this helps.

As a quick check, try this (breakpoint on the "result2 =" line). Your loadOp is redundant in this example, but I did not want to change your code too much:

LoadOperation<Doctor> loadOp = this.ctx.Load(query, loadOperation => 
    { 
        var result2 = loadOp.Entities;
    }, null);

**Note: for those that want to edit this code... Please don't. I wanted to retain the flavour of the asker's code. loadOp and loadOperation point to the same object and result2 was the asker's choice of variable name.*