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Creating a basic EF model

  1. Create a new project using File / New / ASP.NET Core Web Application. Select the Web API template, No Auth, no Docker support.

    Note: If not using Visual Studio, create the project using dotnet new webapi at the cmd line, details as follows:

    1. Create folder ConferencePlanner and call dotnet new sln at the cmd line to create a solution
    2. Create sub-folder BackEnd and create a project using dotnet new webapi at the cmd line inside the folder BackEnd
    3. Add the project to the solution using dotnet sln add BackEnd\BackEnd.csproj
  2. In the BackEnd folder, run dotnet add package Microsoft.EntityFrameworkCore.SqLite if you want to use SqlLite during the workshop (e.g if not on Windows)

  3. Add a new Models folder to the root of the application.

  4. Add a new Speaker class using the following code:

    using System;
    using System.Collections.Generic;
    using System.ComponentModel.DataAnnotations;
    using System.Linq;
    using System.Threading.Tasks;
    using Microsoft.Extensions.DependencyInjection;
    using Microsoft.EntityFrameworkCore.Design;
    
    namespace BackEnd.Models
    {
        public class Speaker
        {
           public int ID { get; set; }
    
           [Required]
           [StringLength(200)]
           public string Name { get; set; }
    
           [StringLength(4000)]
           public string Bio { get; set; }
    
           [StringLength(1000)]
           public virtual string WebSite { get; set; }
        }
    
        public class ApplicationDbContextFactory : IDesignTimeDbContextFactory<ApplicationDbContext>
        {
            public ApplicationDbContext CreateDbContext(string[] args) =>
                Program.CreateWebHostBuilder(args).Build().Services.CreateScope().ServiceProvider.GetRequiredService<ApplicationDbContext>();
        }
    }
  5. Next we'll create a new Entity Framework DbContext. Create a new ApplicationDbContext class in the Models folder using the following code:

    using Microsoft.EntityFrameworkCore;
    using Microsoft.EntityFrameworkCore.Design;
    using Microsoft.EntityFrameworkCore.Infrastructure;
    using Microsoft.Extensions.DependencyInjection;
    
    namespace BackEnd.Models
    {
        public class ApplicationDbContext : DbContext
        {
            public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
                : base(options)
            {
    
            }
    
            public DbSet<Speaker> Speakers { get; set; }
        }
    }
    
  6. Add a connection string to the appSettings.json file for this database:

    {
     "ConnectionStrings": {
       "DefaultConnection": "Server=(localdb)\\mssqllocaldb;Database=aspnet-BackEnd-931E56BD-86CB-4A96-BD99-2C6A6ABB0829;Trusted_Connection=True;MultipleActiveResultSets=true"
     },
     "Logging": {
       "LogLevel": {
         "Default": "Warning"
       }
     },
     "AllowedHosts": "*"
    }

Register the DB Context Service

  1. Add the following code to the top of the ConfigureServices() method in Startup.cs:
    services.AddDbContext<ApplicationDbContext>(options =>
    {
        if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
        {
            options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection"));
        }
        else
        {
            options.UseSqlite("Data Source=conferences.db");
        }
    });

    This code registers the ApplicationDbContext service so it can be injected into controllers. Additionally, it configures operating system specific database technologies and connection strings. To use SqlLite add a reference to the NuGet package Microsoft.EntityFrameworkCore.Sqlite.

Configuring EF Migrations

  1. Open a command prompt and navigate to the project directory. (The directory containing the Startup.cs file).

  2. Run the following commands in the command prompt:

    dotnet build
    dotnet ef migrations add Initial
    dotnet ef database update

Commands Explained

Command Description
dotnet ef migrations add InitialCreate generates code to create the initial database schema based on the model specified in 'ApplicationDbContext.cs'. Initial is the name of the migration.
dotnet ef database update creates the database

For more information on these commands and scaffolding in general, see this tutorial.

A quick look at the Values Controller

First, open the Controllers controller and take a quick look at the ValuesController. You'll see simple functions that correspond to HTTP verbs. You'll see the output of this controller in a bit, but first we'll build our own API controller for the Speakers model class.

Scaffolding an API Controller

Using Visual Studio

  1. Right-click the Controllers folder and select Add/Controller. You'll be shown a prompt for setting up Scaffolding. Select "Minimal Dependencies".
  2. Again, right-click the Controllers folder and select Add/Controller. Select "API Controller with Actions, Using EF".
  3. In the dialog, select the Speaker model for the Model Class, ApplicationDbContext for the "Data Context Class" and click the Add button.

Using the cmd line

  1. Install the aspnet-codegenerator global tool by running the following command:
dotnet tool install --global dotnet-aspnet-codegenerator

Note: You will need to close and reopen the console window to be able to use this tool.

  1. Run the following in the project folder at the cmd line:
    dotnet aspnet-codegenerator controller -api -name SpeakersController -m Speaker -dc BackEnd.Models.ApplicationDbContext -outDir Controllers
    

Testing the API using the Swashbuckle

In this section, we'll be adding documentation to our API using the Swashbuckle NuGet package.

Swashbuckle.AspNetCore is an open source project for generating Swagger documents for Web APIs that are built with ASP.NET Core.

Swagger is a machine readable representation of a RESTful API that enables support for interactive documentation, client SDK generation and discoverability.

Additional information on using Swashbuckle in ASP.NET Core is available in this tutorial: ASP.NET Web API Help Pages using Swagger

  1. Add the Swashbuckle.AspNetCore NuGet package.

    This can be done from the command line using dotnet add package Swashbuckle.AspNetCore

  2. Add the Swashbuckle services in your ConfigureServices method:

    services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
    
    services.AddSwaggerGen(options =>
        options.SwaggerDoc("v1", new Info { Title = "Conference Planner API", Version = "v1" })
    );
  3. Configure Swashbuckle by adding the following lines to top of the Configure method in Startup.cs:

    app.UseSwagger();
    
    app.UseSwaggerUI(options =>
        options.SwaggerEndpoint("/swagger/v1/swagger.json", "Conference Planner API v1")
    );

    Note: Due to how the middleware and pipeline are structured, you'll want to place this before the app.UseMvc() statement.

  4. Run the application (F5 in Visual Studio or dotnet run from console).

  5. Browse to the Swagger UI at http://localhost:<random_port>/swagger.

  6. First, click on the GET button in Values section. You'll see the values that were listed in the ValuesController earlier.

  7. In the Speakers section, click on the GET button. You'll see there are not speakers returned. Let's add one!

  8. In the Speakers section, click on the POST button. Referencing the example on the right, fill in a speaker request. Leave the ID blank, that will be filled in by the database.

  9. When you click the Try it out! button, you should see a success response from the server. Now, clicking the GET button above should show your newly added speaker.

Next: Session #2 - Back-end