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1. Create BackEnd API project.md

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1. Create BackEnd API project.md

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Creating a new project using Visual Studio

  1. Create and add a new project named BackEnd and name the solution ConferencePlanner 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. From the ConferencePlanner folder, add the project to the solution using dotnet sln add BackEnd/BackEnd.csproj

  2. Add a new Models folder to the BackEnd project.

  3. Add a new Speaker class inside the Models folder using the following code:

    using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Threading.Tasks;

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; }
    }
}

  4. Add a reference in the BackEnd project to the NuGet package Microsoft.EntityFrameworkCore.SqlServer version 3.1.3.

    This can be done from the command line in the BackEnd folder using dotnet add package Microsoft.EntityFrameworkCore.SqlServer --version 3.1.3

  5. Add a reference in the BackEnd project to the NuGet package Microsoft.EntityFrameworkCore.Sqlite version 3.1.3.

    This can be done from the command line in the BackEnd folder using dotnet add package Microsoft.EntityFrameworkCore.Sqlite --version 3.1.3

  6. 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;

namespace BackEnd.Models
{
    public class ApplicationDbContext : DbContext
    {
        public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
            : base(options)
        {

        }

        public DbSet<Speaker> Speakers { get; set; }
    }
}

  7. 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",
     "Microsoft": "Warning",
     "Microsoft.Hosting.Lifetime": "Information"
   }
 },
 "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

  2. Ensure the following 'using' statements are at the top of the Startup.cs file to allow the references in our code to work: 
    using BackEnd.Models;
using System.Runtime.InteropServices;
using Microsoft.EntityFrameworkCore;

Configuring EF Migrations

  1. Add a reference to the NuGet package Microsoft.EntityFrameworkCore.Tools version 3.1.3.

    If you're not using Visual Studio install the package from the command line in the BackEnd folder with dotnet add package Microsoft.EntityFrameworkCore.Tools --version 3.1.3

Visual Studio: Package Manager Console

  1. In Visual Studio, select the Tools -> NuGet Package Manager -> Package Manager Console

  2. Run the following commands in the Package Manager Console

    Add-Migration Initial
Update-Database

Command line

  1. Install the EntityFramework global tool dotnet-ef using the following command in the BackEnd folder:

    dotnet tool install -g dotnet-ef --version 3.1.3

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

  3. 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 Initial / Add-Migration Initial 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 / Update-Database creates the database

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

If your database ever gets in a bad state and you'd like to reset things, you can use dotnet ef database drop followed by dotnet ef database update to remove your database and run all migrations again.

A quick look at the Weather Forecast Controller

First, open the Controllers folder and take a quick look at the WeatherForecastController. You'll see a simple function that corresponds to the HTTP GET verb. 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. Select "API Controller with actions, using Entity Framework".
  2. 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 "Microsoft.VisualStudio.Web.CodeGeneration.Design" package

    dotnet add package Microsoft.VisualStudio.Web.CodeGeneration.Design --version 3.1.2

  2. Install the aspnet-codegenerator global tool by running the following command:

    dotnet tool install -g dotnet-aspnet-codegenerator --version 3.1.2

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 a reference to the NuGet package Swashbuckle.AspNetCore version 5.3.0.

    This can be done from the command line using dotnet add package Swashbuckle.AspNetCore --version 5.3.0

  2. Add the Swashbuckle services in your ConfigureServices method:

    services.AddControllers();

services.AddSwaggerGen(options =>
    options.SwaggerDoc("v1", new OpenApiInfo { Title = "Conference Planner API", Version = "v1" })
);

  3. Ensure your Startup.cs file contains the following 'using' statements:

    using Microsoft.OpenApi.Models;
using System.Threading.Tasks;

  4. Configure Swashbuckle by adding the following lines just before UseRouting in the Configure method in Startup.cs:

    app.UseSwagger();

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

  5. Add a MapGet to the beginning of the UseEndpoints statement in the pipeline that redirects requests from the root of our application to the swagger end point.

     app.UseEndpoints(endpoints =>
 {
     endpoints.MapGet("/", context => { 
         context.Response.Redirect("/swagger/");
         return Task.CompletedTask;
     });
     endpoints.MapControllers();
 });

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

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

  8. First, click on the GET button in WeatherForecast section. You'll see the values that were listed in the WeatherForecastController earlier.

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

  10. 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. 

    {
  "name": "Dorothy Gale",
  "bio": "Amateur meteorologist, Oz aficionado, and lead guide for Whirlwind Tours of Kansas",
  "webSite": "https://en.wikipedia.org/wiki/Dorothy_Gale"
}

  11. 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