download source code here

Create project via Cli

Install .net core sdk, .net core runtime at https://www.microsoft.com/net/learn/get-started/windows or https://www.microsoft.com/net/download/windows
in Feb, 2018, .net core sdk is v2.1.4, .net core runtime is v 2.0.5
open console, dotnet new --help to check templates
create webapi project, dotnet new webapi -o myApi
run the app, dotnet run
install entity framework core package. dotnet add Microsoft.EntityFrameworkCore.SqlServer
other commands:
dotnet add package: Adds a package reference to the project file, then runs dotnet restore to install the package. dotnet remove package: Removes a package reference from the project file dotnet restore: Restores the dependencies and tools of a project. dotnet nuget locals: Clears or lists local NuGet resources such as the http-request cache, the temporary cache, and the machine-wide global packages folder.

Create project via Visual Studio

we got

If this webapi project references other libaries, make sure to choose the compatible .net framework version

ctrl + f5 to run,

nuget > install Microsoft.EntityFrameworkCore.SqlServer package

Create a simple demo

add models

Models > TodoItem.cs:

 namespace Models
 {
     public class TodoItem
     {
         public long Id { get; set; }
         public string Name { get; set; }
         public bool IsComplete { get; set; }
     }
 }

add data

Data > TodoContext.cs:

 using Microsoft.EntityFrameworkCore;
 using Models;

 namespace TodoApi.Models
 {
     public class TodoContext : DbContext
     {
         public TodoContext(DbContextOptions<TodoContext> options)
             : base(options)
         {
         }
	
         public DbSet<TodoItem> TodoItems { get; set; }
	
     }
 }

register db context in dependency injection container. Here we specify an in-memory database is injected into the service container.

update Startup.cs

 public class Startup
 {       
     public void ConfigureServices(IServiceCollection services)
     {
         services.AddDbContext<TodoContext>(opt => opt.UseInMemoryDatabase("TodoList"));
         services.AddMvc();
     }
     ...
 }

Create a controller: TodoController.cs

 using Microsoft.AspNetCore.Mvc;
 using Models;
 using Data;
 using System.Linq;
	
 namespace TodoApi.Controllers
 {
     [Route("api/[controller]")]
     public class TodoController : Controller
     {
         private readonly TodoContext _context;
	
         public TodoController(TodoContext context)
         {
             _context = context;
	
             if (_context.TodoItems.Count() == 0)
             {
                 _context.TodoItems.Add(new TodoItem { Name = "Item1" });
                 _context.SaveChanges();
             }
         }
     }
 }

Add get endpoints

 [HttpGet]
 public IEnumerable<TodoItem> GetAll()
 {
     return _context.TodoItems.ToList();
 }
	
 [HttpGet("{id}", Name = "GetTodo")]
 public IActionResult GetById(long id)
 {
     var item = _context.TodoItems.FirstOrDefault(t => t.Id == id);
     if (item == null)
     {
         return NotFound();
     }
     return new ObjectResult(item);
 }

Add create endpoint

 [HttpPost]
 public IActionResult Create([FromBody] TodoItem item)
 {
     if (item == null)
     {
         return BadRequest();
     }
	
     _context.TodoItems.Add(item);
     _context.SaveChanges();
	
     return CreatedAtRoute("GetTodo", new { id = item.Id }, item);
 }

Add update endpoint

 [HttpPut("{id}")]
 public IActionResult Update(long id, [FromBody] TodoItem item)
 {
     if (item == null || item.Id != id)
     {
         return BadRequest();
     }
	
     var todo = _context.TodoItems.FirstOrDefault(t => t.Id == id);
     if (todo == null)
     {
         return NotFound();
     }
	
     todo.IsComplete = item.IsComplete;
     todo.Name = item.Name;
	
     _context.TodoItems.Update(todo);
     _context.SaveChanges();
     return new NoContentResult();
 }

add delete endpoint

 [HttpDelete("{id}")]
 public IActionResult Delete(long id)
 {
     var todo = _context.TodoItems.FirstOrDefault(t => t.Id == id);
     if (todo == null)
     {
         return NotFound();
     }
	
     _context.TodoItems.Remove(todo);
     _context.SaveChanges();
     return new NoContentResult();
 }

Enable cors

Install package Microsoft.AspNetCore.Cors either via nuget in visual studio or command line

Enable cors

way1, enable in middleware. modify Startup.cs

 public void ConfigureServices(IServiceCollection services)
 {
     services.AddCors();
 }

way2, enable in controller

Add lazy loading

Install package Microsoft.EntityFrameworkCore.Proxies
Suppose we have a database EmployeeManagement, we use database first to generate model classes:
Scaffold-DbContext "Server=(local);Database=EmployeeManagement;Integrated Security=True;" Microsoft.EntityFrameworkCore.SqlServer -OutputDir Entities
A folder Entities will be created with entities and dbcontext in it
Open entity classes, manually set all navigation properties as virtual:

Enable lazy loading, Startup.cs

 ```
 ...
  public void ConfigureServices(IServiceCollection services)
         {
             // add db optoins
             var connection = @"Server=(local);Database=EmployeeManagement;Integrated Security=true;";
             services.AddDbContext<EmployeeManagementContext>(opt =>
                 {
                     opt.UseLazyLoadingProxies().UseSqlServer(connection);
                 }
             );
             //services.AddEntityFrameworkProxies();
             services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
         }
 ```

Test

run via dotnet run
navigate to http://localhost:5000/api/todo
post a json data
{ “id”: 2, “name”: “Item2”, “isComplete”: true }

Add database first entities

Add nuget libraries:

 Microsoft.EntityFrameworkCore.SqlServer
 EntityFrameworkCore.Tools
 EntityFrameworkCore.SqlServer.Design

nuget command console Scaffold-DbContext "Server=(local)\SQLEXPRESS;Database=EFCoreDBFirstDemo;Integrated Security=True;" Microsoft.EntityFrameworkCore.SqlServer -OutputDir Entities
it will create a Entities folder with all models from database inside it.

Enable cors

Install Microsoft.AspNetCore.Cors package

Add the CORS services

 public void ConfigureServices(IServiceCollection services)
 {
     ...
     services.AddCors();
 } 

Enable cors with middleware. Note that the CORS middleware must precede any defined endpoints in your app that you want to support cross-origin requests (ex. before any call to UseMvc).

 public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
 {
     loggerFactory.AddConsole();
	
     if (env.IsDevelopment())
     {
         app.UseDeveloperExceptionPage();
     }
	
     // Shows UseCors with CorsPolicyBuilder.
     app.UseCors(builder =>
        builder.AllowAnyOrigin().AllowAnyHeader().AllowAnyMethod());
	
     ...
 }

Model validation

Attribute validation

modify properties of model

We can define our own validation attribute

 public class TorontoPhoneAttribute : System.ComponentModel.DataAnnotations.ValidationAttribute
 { 

     protected override ValidationResult IsValid(object value, ValidationContext validationContext)
     {
         if(!value.ToString().StartsWith("647"))
         {
             return new ValidationResult("this is not 647-xxx-xxxx");
         }
         return null;
     }
 }

In controller, verify ModelStatus.IsValid and return badrequest accordingly

 [HttpPost("")]
 public IActionResult AddCompany([FromBody] TblCompany company)
 {
     if (ModelState.IsValid)
     {
         this.employeeManagementV2Context.TblCompany.Add(company);
         this.employeeManagementV2Context.SaveChanges();
         return Ok();
     }
     return BadRequest(ModelState);
 }