ADO.NET Data Services: Creating a custom Data Context #2: The Client

In part 1 I showed how to create a simple in-memory custom data context for ADO.NET Data Services. Creating a managed client is also very simple. First we need to provide a similar domain model to our server. In this case the classes are identical except that now Teacher has a List<Course> rather than a simple array (Course[]) as it's Courses property:

using System.Collections.Generic;

namespace Mike.DataServices.Client.Model
{
   public class Teacher
   {
       public int ID { get; set; }
       public string Name { get; set; }
       public List<Course> Courses { get; set; }
   }
}

Next I wrote a class to extend DataServiceContext with properties for Teachers and Courses that are both DataServiceQuery<T>. Both DataServiceContext and DataServiceQuery<T> live in the System.Data.Services.Client assembly. You don't have to create this class, but it makes the subsequent use of the DataServiceContext simpler. You can also use use the 'Add Service Reference' menu item, but I don't like the very verbose code that this generates.

using System;
using System.Data.Services.Client;
using Mike.DataServices.Client.Model;

namespace Mike.DataServices.Client
{
   public class SchoolServiceProxy : DataServiceContext
   {
       private const string url = "http://localhost:4246/SchoolService.svc";

       public SchoolServiceProxy() : base(new Uri(url))
       {
       }

       public DataServiceQuery<Teacher> Teachers
       {
           get
           {
               return CreateQuery<Teacher>("Teachers");
           }
       }

       public DataServiceQuery<Course> Courses
       {
           get
           {
               return CreateQuery<Course>("Courses");
           }
       }
   }
}

Here's a simple console program that outputs teacher John Smith and his courses and then the complete list of courses. The nice thing is that DataServiceQuery<T> implements IQueryable<T> so we can write LINQ queries against our RESTfull service.

using System;
using System.Linq;
using System.Data.Services.Client;
using Mike.DataServices.Client.Model;

namespace Mike.DataServices.Client
{
   class Program
   {
       readonly SchoolServiceProxy service = new SchoolServiceProxy();

       static void Main(string[] args)
       {
           var program = new Program();
           program.GetJohnSmith();
           program.GetAllCourses();
       }

       public void GetJohnSmith()
       {
           Console.WriteLine("\r\nGetJohnSmith");

           var teachers = service.Teachers.Where(c => c.Name == "John Smith");

           foreach (var teacher in teachers)
           {
               Console.WriteLine("Teacher: {0}", teacher.Name);

               // N+1 issue here
               service.LoadProperty(teacher, "Courses");

               foreach (var course in teacher.Courses)
               {
                   Console.WriteLine("\tCourse: {0}", course.Name);
               }
           }
       }

       public void GetAllCourses()
       {
           Console.WriteLine("\r\nGetAllCourses");

           var courses = service.Courses;

           foreach (var course in courses)
           {
               Console.WriteLine("Course: {0}", course.Name);
           }
       }
   }
}

We get this ouput:

Code is here:

http://static.mikehadlow.com/Mike.DataServices.InMemory.zip