Trackable Entities for EF Core Sample

Sample solution using Trackable Entities with ASP.NET Core and Entity Framework Core.

Steps

Note: Perform the following steps to create an end-to-end solution using Trackable Entities with a REST-ful ASP.NET Core web api service and a client .NET console application. To see the final outcome of this process, please refer to the code in this repository.

1. Create the NorthwindSlim sample database.
2. Generate server-side trackable entities.
3. Link to generated entities from a NetStandard project.
4. Add an ASP.NET Core web api project and use EF Core Migrations to create a new database from the generated entities.
5. Install the TrackableEntities.EF.Core NuGet package and add web api controllers with GET, POST, PUT and DELETE actions.
6. Generate client-side trackable entities in a traditional class library project.
7. Add a traditional .NET client console application that uses the TrackableEntities.Client NuGet package to perform client-side change tracking, sending object graphs of changed entities to the Web API service where they are saved to the database in a single transaction.

NorthwindSlim Database

This sample shows how you can both generate entities from an existing database (database-first) and create a new database from existing entities (code-first). In real life you would do either one or the other.

• This sample uses a skinny version of the Northwind sample database, called NorthwindSlim, which you can download from http://bit.ly/northwindslim.
• Open SQL Server Management Studio, connect to (localdb)\MsSqlLocalDb and create a new database named NorthwindSlim. Then run the NorthwindSlim.sql file, which will create all the database tables and populate them with data.

Server-Side Generated Trackable Entities

Entities are generated with a traditional .NET class library so that you can use the Visual Studio wizard for adding an ADO.NET Entity Data Model, which uses custom T4 templates to generate server-side trackable entities.

Note: If you haven't done so already, create a Visual Studio solution either prior to or while adding a class library project.

• Add a .NET 4.6.1 Class Library project called NetCoreSample.Entities.Generated.
  • Open project prpoperties and remove ".Generated" from the default namespace.
• Add a Data Connection in Visual Studio pointing to the NorthwindSlim database on (localdb)\MsSqlLocalDb.
• Install NuGet packages:
  • EntityFramework
  • Install TrackableEntities.Common.Core -Pre
  • TrackableEntities.CodeTemplates.Service.Net45

  Note: Ignore the compiling transformation error.

• Edit EntityType.cs.t4 file in the CodeTemplates/EFModelFromDatabase folder.
  • First go to Tools, Extensions and Updates, and install the Tangible T4 Editor.
  • Remove the following namespace import: using System.Data.Entity.Spatial
  • Update the TrackableEntities namespace import to: using TrackableEntities.Common.Core
• Add a new Item, select Data, then ADO.NET Entity Data Model, and name it NorthwindSlim.
  • Choose Code First from Database, then select the NorthwindSlim data connection you created earlier.
  • Select all the tables and click Finish.
  • Build the project.

Trackable Entities NetStandard Library

• Add a NetStandard class library called NetCoreSample.Entities
  • Install NuGet package: TrackableEntities.Common.Core -Pre
• Add a reference to System.ComponentModel.DataAnnotations.
• Link generated entities from the NetCoreSample.Entities.Generated project.
  • Right-click NetCoreSample.Entities project, select Add New Item
  • Nviate to the Generated entities project and select all .cs files except NorthwindSlim.cs.
  • From the Add button dropdown select Add As Link.
  • Build the project.

EF Core Migrations

In this section you will create a new database based on entities generated from the NorthwindSlim database.

Note: To perform an EF Core migration you need to first create either an ASP.NET Core app or a .NET Core console app. It is not possible to use a class library for EF Core migrations.

• Add a new ASP.NET Core web application

  • Select Web API template targeting .NET Core with ASP.NET Core 2.0.

• Install NuGet packages:

  • Microsoft.EntityFrameworkCore.SqlServer
  • TrackableEntities.EF.Core -Pre
  • Microsoft.EntityFrameworkCore.Tools

• Add a reference from the Web project to the Entities project.

  • Then build the solution.

• Edit the Web csproj file to add the following to the last ItemGroup

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

• Add an App_Data directory to the Web project.

• Update appsettings.json to add a connection string to a local database file

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

• Add a NorthwindSlimContext class to the Web project.

  public class NorthwindSlimContext : DbContext
  {
      public NorthwindSlimContext(DbContextOptions<NorthwindSlimContext> options) : base(options) { }
  
      public DbSet<Category> Categories { get; set; }
      public DbSet<Customer> Customers { get; set; }
      public DbSet<Order> Orders { get; set; }
      public DbSet<OrderDetail> OrderDetails { get; set; }
      public DbSet<Product> Products { get; set; }
  }

• Add a NorthwindSlimContextFactory class to the Web project.

  public class NorthwindSlimContextFactory : IDesignTimeDbContextFactory<NorthwindSlimContext>
  {
      public NorthwindSlimContext CreateDbContext(string[] args)
      {
          var optionsBuilder = new DbContextOptionsBuilder<NorthwindSlimContext>();
          optionsBuilder.UseSqlServer(
              "Data Source=(localdb)\\MSSQLLocalDB;initial catalog=NetCoreSample;Integrated Security=True; MultipleActiveResultSets=True");
          return new NorthwindSlimContext(optionsBuilder.Options);
      }
  }

• Add an initial migration.

  • Open command prompt at Web project to add an initial migration.

  dotnet ef migrations add Initial
  

• Use the ef tools to create the database.

  dotnet ef database update
  

• Configure services for DI

  • Add code in Startup.ConfigureServices to add the DbContext class

  var connectionString = Configuration.GetConnectionString("NetCoreSample");
  services.AddDbContext<NorthwindSlimContext>(options => options.UseSqlServer(connectionString));

Web API Controllers

This sample uses the .NET Core CLI for scaffolding Web API contollers with GET, POST, PUT and DELETE actions that use Entity Framework Core for persisting changes to the database in a disconnected manner.

• Update Startup.ConfigureServices to handle cyclical references when serializing JSON.

  services.AddMvc()
      .AddJsonOptions(options =>
          options.SerializerSettings.PreserveReferencesHandling = PreserveReferencesHandling.All);

• Use the DotNet CLI to scaffold a Customer controller.

  • Install NuGet package: Microsoft.VisualStudio.Web.CodeGeneration.Design
  • Open a command prompt at the Web project location and run the following:

  dotnet aspnet-codegenerator --project . controller -name CustomerController -api -outDir Controllers -m Customer -dc NorthwindSlimContext
  

  • Remove actions in CustomerController except GetCustomers and GetCustomer.
  • Refactor GetCustomers as an async action.

  [HttpGet]
  public async Task<IActionResult> GetCustomers()
  {
      var customers = await _context.Customers
          .ToListAsync();
      return Ok(customers);
  }

  • Run the Web project by pressing Ctrl+F5 and navigate to api/customer and api/customer/ALFKI.

• Add an Order controller.

  dotnet aspnet-codegenerator --project . controller -name OrderController -api -outDir Controllers -m Order -dc NorthwindSlimContext
  

  • Refactor GetOrders as an async action with includes.

  [HttpGet]
  public async Task<IActionResult> GetOrders()
  {
      var orders = await _context.Orders
          .Include(m => m.Customer)
          .Include(m => m.OrderDetails)
          .ThenInclude(m => m.Product)
          .ToListAsync();
      return Ok(orders);
  }

  • Also add includes to GetOrder.

  var order = await _context.Orders
      .Include(m => m.Customer)
      .Include(m => m.OrderDetails)
      .ThenInclude(m => m.Product)
      .SingleOrDefaultAsync(m => m.OrderId == id);

  • Navigate to api/order and api/order/1.

  • Add a GetOrders overload that filters by customerId.

  // GET: api/Order/ALFKI
  [HttpGet("{customerId:alpha}")]
  public async Task<IActionResult> GetOrders([FromRoute] string customerId)
  {
      var orders = await _context.Orders
          .Include(m => m.Customer)
          .Include(m => m.OrderDetails)
          .ThenInclude(m => m.Product)
          .Where(m => m.CustomerId == customerId)
          .ToListAsync();
      return Ok(orders);
  }

  • Navigate to api/order/ALFKI.

• Refactor Put, Post and Delete actions to call _context.ApplyChanges.

  • Refactor PutOrder to replace setting state to Modified with applying changes nad return the order with an OK response.

  //_context.Entry(order).State = EntityState.Modified;
  _context.ApplyChanges(order);
  
  // Populate reference properties
  await _context.LoadRelatedEntitiesAsync(order);
  
  // Reset tracking state to unchanged
  _context.AcceptChanges(order);
  
  //return NoContent();
  return Ok(order);

  • Refactor PostOrder to set TrackingState to Added and apply changes.
  • Remove the id parameter from PostOrder.

  // Set state to added
  order.TrackingState = TrackingState.Added;
  
  // Apply changes to context
  _context.ApplyChanges(order);
  
  // Persist changes
  await _context.SaveChangesAsync();
  
  // Populate reference properties
  await _context.LoadRelatedEntitiesAsync(order);
  
  // Reset tracking state to unchanged
  _context.AcceptChanges(order);

  • Refactor DeleteOrder to set TrackingState to Deleted and apply changes, and return Ok without an entity.

  // Retrieve order with details
  var order = await _context.Orders
      .Include(m => m.OrderDetails)
      .SingleOrDefaultAsync(m => m.OrderId == id);
  if (order == null)
  {
      return NotFound();
  }
  
  // Set tracking state to deleted
  order.TrackingState = TrackingState.Deleted;
  
  // Detach object graph
  _context.DetachEntities(order);
  
  // Apply changes to context
  _context.ApplyChanges(order);
  
  // Persist changes
  await _context.SaveChangesAsync();
  
  return Ok();

Client-Side Generated Trackable Entities

Client-side entities are generated using the Visual Studio wizard for adding an ADO.NET Entity Data Model, even though the client does not require any reference to Entity Framework.

• Add a .NET 4.6.1 class library project called NetCoreSample.Entities.Client.
• Install NuGet packages:
  • EntityFramework
  • TrackableEntities.Client
  • TrackableEntities.CodeTemplates.Client.Net45
• Add new item, Data, ADO.NET Entity Data Model.
  • Select the NorthwindSlim data connection

Client Console Application

The client console app uses traditional Trackable Entities NuGet packages, which perform client-side change tracking for marking entities as Added, Modified or Deleted.

• Add a .NET 4.6.1 console app called NetCoreSample.ConsoleClient.
• Install NuGet packages:
  • TrackableEntities.Client
  • Microsoft.AspNet.WebApi.Client
  • AspNetWebApi2Helpers.Serialization
• Reference the Entities.Client project.
• Add private helper methods.
• Add code to retrieve and update entities.
  • Retrieve customers
  • Retrieve customer orders
  • Create an order with details
  • Update an existing order with unchanged, added, modified and deleted details
  • Delete an order and verify that it was deleted

Note: Complete code for the client app can be found in the ConsoleClient project of the provided solution.