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ASP.NET Core minimal APIs

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2 minutes to read

A single file ASP.NET Core minimal APIs

Install .NET on WSL2 Ubuntu

Follow this instruction to install .NET on WSL2.

Create todo app API project

Create a new ASP.NET Core minimal APIs project

  • Create a new project from a template with the following command:
      dotnet new web -o MinimalApi
  • This will create a new ASP.NET Core minimal API inside a MinimalApi folder.
  • CD to a MinimalApi folder and open it with VS Code by executing code ..
      cd MinimalApi
      code .

Current project structure

  • Optionally, you can check project file structure with tree command.
      tree MinimalApi -I 'bin|obj'
      MinimalApi
      ├── MinimalAPI.csproj
      ├── Program.cs
      ├── Properties
      │   └── launchSettings.json
      ├── appsettings.Development.json
      └── appsettings.json

Run the project

  • Open Program.cs with VS Code and edit it to pass http://localhost:3000 to app.Run method.
    // Program.cs
    // ...
        app.Run("http://localhost:3000");
    // ...
  • Open a VS Code's integrated terminal and run:
      dotnet run
  • Open a browser and navigate to http://localhost:3000, you should see Hello World! message on a home page.

Install packages for using EF Core ORM

  • In an integrated terminal, run the following commands:
      dotnet add package Microsoft.EntityFrameworkCore --version 6.0.4
      dotnet add package Microsoft.EntityFrameworkCore.InMemory --version 6.0.4

Create a single file todo app API

  • Replace contents of Program.cs with the following source code:

      // Program.cs
      using Microsoft.EntityFrameworkCore;
      // Create a builder.
      var builder = WebApplication.CreateBuilder(args);
      // Configure EF to use in-memory database, for testing purpose only.
      builder.Services.AddDbContext<TodoDbContext>(
          options => options.UseInMemoryDatabase("TodoItems")
      );
      // Create a new web app.
      using var app = builder.Build();
      if (app.Environment.IsDevelopment())
      {
          app.UseDeveloperExceptionPage();
      }
      // https://docs.microsoft.com/en-us/aspnet/core/fundamentals/minimal-apis?view=aspnetcore-6.0#responses
      app.MapGet("/", (Func<string>)(() => "Hello World!"));
      app.MapGet("/todos", async (HttpContext http, TodoDbContext todoContext) =>
      {
          var todos = await todoContext.TodoItems.ToListAsync();
          return todos;
      });
      app.MapGet("/todos/{id}", async (HttpContext http, TodoDbContext todoContext, int? id) =>
      {
          if (!id.HasValue)
          {
              return Results.BadRequest();
          }
          var todo = await todoContext.TodoItems.FindAsync(id);
          if (todo == null)
          {
              return Results.NotFound();
          }
          return Results.Ok(todo);
      });
      app.MapPost("/todos", async (HttpContext http, TodoDbContext dbContext, TodoItem todo) =>
      {
          dbContext.TodoItems.Add(todo);
          await dbContext.SaveChangesAsync();
          http.Response.StatusCode = 201; // Created
      });
      app.MapPut("/todos/{id}", async (HttpContext http, TodoDbContext dbContext, TodoItem changedTodo, int? id) =>
      {
          if (!id.HasValue)
          {
              return Results.BadRequest();
          }
          var exisingTodo = await dbContext.TodoItems.FindAsync(id);
          if (exisingTodo == null)
          {
              return Results.NotFound();
          }
          exisingTodo.Title = changedTodo.Title;
          exisingTodo.IsCompleted = changedTodo.IsCompleted;
          await dbContext.SaveChangesAsync();
          return Results.NoContent();
      });
      app.MapDelete("/todos/{id}", async (HttpContext http, TodoDbContext dbContext, int? id) =>
      {
          if (!id.HasValue)
          {
              return Results.BadRequest();
          }
          var todo = await dbContext.TodoItems.FindAsync(id);
          if (todo == null)
          {
              return Results.NotFound();
          }
          dbContext.TodoItems.Remove(todo);
          await dbContext.SaveChangesAsync();
          return Results.NoContent();
      });
      app.Run("http://localhost:3000");
      // Define TodoItem model
      class TodoItem
      {
          public int Id { get; set; }
          public string Title { get; set; }
          public bool IsCompleted { get; set; }
          public TodoItem(string title) => Title = title;
      }
      // Define TodoDbContext
      class TodoDbContext : DbContext
      {
          public TodoDbContext(DbContextOptions options) : base(options) { }
          public DbSet<TodoItem> TodoItems => Set<TodoItem>();
      }

  • Save the file.

Run todo app API

  • In an integrated terminal, run the following command. (Kill the running process if needed.):
      dotnet run
  • You can now test APIs with any client tools, e.g. Postman.
  • All available APIs:
    • Use http://localhost:3000/todos with HTTP GET to get all existing todo items.
    • Use http://localhost:3000/todos/{id} with HTTP GET to get an existing todo item.
    • Use http://localhost:3000/todos with HTTP POST to add a new todo item.
    • Use http://localhost:3000/todos/{id} with HTTP PUT to update an existing todo item.
    • Use http://localhost:3000/todos/{id} with HTTP DELETE to delete an existing todo item.

Useful information and credit

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