tonysneed / Demo.ODataAspNetCore

OData for ASP.NET Core Proof-of-Concept

Proof-of-Concept for OData for ASP.NET Core

1. Create a new ASP.NET Core Web API

   • Using Visual Studio, create a new ASP.NET Core web project
   • Select the Web API template
   • Add global.json file to lock down .NET Core SDK version

   dotnet new globaljson
   

   {
     "sdk": {
       "version": "2.1.2"
     }
   }

2. Scaffold Product table from NorthwindSlim database

   • Create NorthwindSlim database on LocalDb SQL Server instance
   • Download and run script from http://bit.ly/northwindslim
   • Add package for Microsoft.EntityFrameworkCore.SqlServer.
   • Edit the csproj file and add the following element to the last ItemGroup:

   <DotNetCliToolReference Include="Microsoft.EntityFrameworkCore.Tools.DotNet" Version="2.0.0" />

   • Execute dotnet restore from the command line.
   • Reverse engineer the Product table from NorthwindSlim.

   dotnet ef dbcontext scaffold "Data Source=(localdb)\MSSQLLocalDB; Initial Catalog=NorthwindSlim; Integrated Security=True" Microsoft.EntityFrameworkCore.SqlServer -o Models -c NorthwindSlimContext -f -t Product
   

   • Two files will be added to a Models folder: NorthwindSlimContext.cs, Product.cs

3. Update the NorthwindSlimContext class

   • Remove the OnConfiguring method.
   • Add a NorthwindSlimContextEx.cs file with a ctor.

   using Microsoft.EntityFrameworkCore;
   
   namespace ODataAspNetCorePoc.Models
   {
   	public partial class NorthwindSlimContext
   	{
   		public NorthwindSlimContext(DbContextOptions<NorthwindSlimContext> options) : base(options) { }
   	}
   }

4. Configure the web api to use the EF context and connection string.

   • Add a connection string to appsettings.json.

   "ConnectionStrings": {
   "NorthwindContext": "Data Source=(localdb)\\MSSQLLocalDB;initial catalog=NorthwindSlim;Integrated Security=True; MultipleActiveResultSets=True"
   }

   • Update the ConfigureServices method in Startup.cs.

   public void ConfigureServices(IServiceCollection services)
   {
   	services.AddMvc();
   	var connectionString = Configuration.GetConnectionString("NorthwindContext");
   	services.AddDbContext<NorthwindSlimContext>(options => options.UseSqlServer(connectionString));
   }

5. Add support for OData to the Web API project.

   • Add a NuGet package source for the OData ASP.NET Core nightly builds.

   https://www.myget.org/F/webapinetcore/
   

   • You can use the Package Manager Console to install the OData package:

   Install-Package Microsoft.AspNetCore.OData -pre
   

   • Add the following line of code in ConfigureServices before services.AddMvc():

   services.AddOData();

   • Add a private GetEdmModel method to Startup.cs.

   private IEdmModel GetEdmModel(IServiceProvider serviceProvider)
   {
   	var builder = new ODataConventionModelBuilder(serviceProvider);
   	builder.EntitySet<Product>("Product");
   	return builder.GetEdmModel();
   }

   Note: Resolve IEdmModel by adding: using Microsoft.OData.Edm.

   • Update the Configure method as follows:

   public void Configure(IApplicationBuilder app, IHostingEnvironment env)
   {
   	if (env.IsDevelopment())
   	{
   		app.UseDeveloperExceptionPage();
   	}
   
   	IEdmModel model = GetEdmModel(app.ApplicationServices);
   	app.UseMvc(routes =>
   		{
   			routes.MapODataServiceRoute("odata_route", "odata", model);
   			routes.MapRoute(
   				name: "default",
   				template: "{controller=Home}/{action=Index}/{id?}");
   		});
   }

   • Change launchUrl in launchSettings.json to "odata".
   • Press F5 or Ctrl+F5 to launch the app.
   • You should see the following in the browser.

   {
     @odata.context: "http://localhost:54151/odata/$metadata",
     value: [
     	{
   	  name: "Product",
   	  kind: "EntitySet",
   	  url: "Product"
       }
     ]
   }

6. Add a ProductController.cs file to the Controllers folder.

   • Add the following attribute: [Produces("application/json")]
   • Inherit from ODataController.
   • Inject a NorthwindSlimContext into a constructor.
   • Add a Get method returning IQueryable with a [EnableQuery] attribute.

   [Produces("application/json")]
   public class ProductController : ODataController
   {
   	private readonly NorthwindSlimContext _context;
   
   	public ProductController(NorthwindSlimContext context)
   	{
   		_context = context;
   	}
   
   	[HttpGet]
   	[EnableQuery]
   	public IQueryable<Product> Get()
   	{
   		return _context.Product;
   	}
   }

   • Submit a GET request to http://localhost:54151/odata/Product
   • You should get back a Product array.

7. Add a POST action to the Product controller.

   [HttpPost]
   public async Task<IActionResult> Post([FromBody]Product item)
   {
   	if (!ModelState.IsValid)
   	{
   		return BadRequest(ModelState);
   	}
   
   	_context.Entry(item).State = EntityState.Added;
   
   	try
   	{
   		await _context.SaveChangesAsync();
   	}
   	catch (DbUpdateException)
   	{
   		if (ItemExists(item.ProductId))
   		{
   			return StatusCode((int)HttpStatusCode.Conflict);
   		}
   		throw;
   	}
   
   	return Created(item);
   }
   
   private bool ItemExists(int id)
   {
   	return _context.Product.Any(e => e.ProductId == id);
   }

   • Submit a POST request via Postman or Fiddler with a Content-Type header of application/json.

   {
   	"ProductName": "Chocolato",
   	"CategoryId": 1,
   	"UnitPrice": 24,
   	"Discontinued": false,
   }

   • You should receive a 201 response with the inserted product.

Note: Put, Patch and Delete actions presently return a 404 Not Found response.