ASP.NET WebApi

ASP.NET see: https://github.com/boeschenstein/aspnet

Routing

Add relative sub routes

[ApiController]
[Route('api/mainroute')]
public class MyControllerClass ...

    [HttpPost('my/additional/subroute1')]
    public async Task<IActionResult> MyEndpoint1Async ...

    [Authorize(Policy = PfwPolicyRequirement.EditorOrAdmin)]
    //[ProducesDefaultResponseType] todo what is this ?
    [ProducesResponseType(StatusCodes.Status204NoContent)]
    [ProducesResponseType(typeof(IReadOnlyCollection<string>), StatusCodes.Status400BadRequest)]
    [ProducesResponseType(typeof(IReadOnlyCollection<string>), StatusCodes.Status404NotFound)]
    [Produces("application/octet-stream")]
    [HttpGet('my/additional/subroute2/{id:Guid}', Name = 'anothername')]
    public async Task<IActionResult> MyEndpoint2Async ...

Move Controllers to other project/assembly

Option 1)

Use ASP.NET Core APIs in a class library. Add this to your csproj:

  <!-- Use ASP.NET Core APIs in a class library -->
  <!-- https://learn.microsoft.com/en-us/aspnet/core/fundamentals/target-aspnetcore -->
  <ItemGroup>
    <FrameworkReference Include="Microsoft.AspNetCore.App" />
  </ItemGroup>

Option b)

program.cs:

var presentationAssembly = typeof(PresentationProj.AssemblyReference).Assembly;

// AddControllers() needs <FrameworkReference Include="Microsoft.AspNetCore.App" />
services.AddControllers().AddApplicationPart(presentationAssembly);

• Source: Clean Architecture With .NET 6 And CQRS - Project Setup by Milan Jovanović https://youtu.be/tLk4pZZtiDY Min 11:20
• Docs: https://learn.microsoft.com/en-us/aspnet/core/mvc/advanced/app-parts

This approach might need some nugets:

<PackageReference Include="Microsoft.Extensions.Hosting.Abstractions" Version="8.0.0" />
<PackageReference Include="Microsoft.AspNetCore.Components" Version="8.0.5" />

Order of Middleware

The order that middleware components are added in the Program.cs file defines the order in which the middleware components are invoked on requests (and the reverse order for the response). The order is critical for security, performance, and functionality.

Use this recommended order:

• Start: Request
• ExceptionHandler
• HSTS
• HttpsRedirection (avoid this anyway: can do harm in OIDC scenario: does not forward security headers)
• Static Files
• Routing
• CORS
• Authentication
• Authorization
• Custom middlewares
• Endpoint

Source: https://learn.microsoft.com/en-us/aspnet/core/fundamentals/middleware/?view=aspnetcore-8.0#middleware-order

File Download

Zip, using efficiant streams

https://swimburger.net/blog/dotnet/create-zip-files-on-http-request-without-intermediate-files-using-aspdotnet-mvc-razor-pages-and-endpoints

[HttpGet]
[ProducesResponseType(StatusCodes.Status200OK)]
[Produces("application/octet-stream")]
[Route("download0", Name = "zipfile")]
public async Task DownloadBots()
{
    Response.ContentType = "application/octet-stream";
    Response.Headers.Add("Content-Disposition", "attachment; filename=\"Bots.zip\"");

    var botsFolderPath = Path.Combine("c:\\temp", "bots");
    var botFilePaths = Directory.GetFiles(botsFolderPath);
    using (ZipArchive archive = new ZipArchive(Response.BodyWriter.AsStream(), ZipArchiveMode.Create))
    {
        foreach (var botFilePath in botFilePaths)
        {
            var botFileName = Path.GetFileName(botFilePath);
            var entry = archive.CreateEntry(botFileName);
            using (var entryStream = entry.Open())
            using (var fileStream = System.IO.File.OpenRead(botFilePath))
            {
                await fileStream.CopyToAsync(entryStream);
            }
        }
    }
}

CSV using CSVHelper (stream only, no files)

Inspired from https://stackoverflow.com/questions/13646105/csvhelper-not-writing-anything-to-memory-stream/22997765#22997765

[HttpGet]
[ProducesResponseType(StatusCodes.Status200OK)]
[Produces("application/octet-stream")]
[Route("download1", Name = "mycsv")]
public void DownloadCsv()
{
    Response.ContentType = "application/octet-stream";
    Response.Headers.Add("Content-Disposition", "attachment; filename=\"mycsv.csv\"");

    using (var streamWriter = new StreamWriter(Response.BodyWriter.AsStream()))
    using (var csvWriter = new CsvWriter(streamWriter, CultureInfo.InvariantCulture))
    {
        csvWriter.WriteRecords<User>(users);
        csvWriter.Flush();
    } // StreamWriter gets flushed here.
}

No CSVHelper

from https://arminzia.com/blog/export-data-to-excel-with-aspnet-core/

[HttpGet]
[ProducesResponseType(StatusCodes.Status200OK)]
[Produces("application/octet-stream")]
[Route("download2", Name = "usercsvfile")]
public IActionResult Csv()
{
    var builder = new StringBuilder();
    builder.AppendLine("Id,Username,Email,JoinedOn,SerialNumber");
    foreach (var user in users)
    {
        builder.AppendLine($"{user.Id},{user.Username},{user.Email},{user.JoinedOn.ToShortDateString()},{user.SerialNumber}");
    }
    return File(Encoding.UTF8.GetBytes(builder.ToString()), "text/csv", "users.csv");
}

Data classes:

    public class User
    {
        public int Id { get; set; }
        public string Username { get; set; }
        public string Email { get; set; }
        public string SerialNumber { get; set; }
        public DateTime JoinedOn { get; set; }
    }

    private readonly List<User> users = new()
    {
      new User
      {
          Id = 1,
          Username = "ArminZia",
          Email = "[email protected]",
          SerialNumber = "NX33-AZ47",
          JoinedOn = new DateTime(1988, 04, 20)
      },
      new User
      {
          Id = 2,
          Username = "DoloresAbernathy",
          Email = "[email protected]",
          SerialNumber = "CH1D-4AK7",
          JoinedOn = new DateTime(2021, 03, 24)
      }
    };

Information

• Handle errors in ASP.NET Core controller-based web APIs
  • UseExceptionHandler, UseStatusCodePages: https://learn.microsoft.com/en-us/aspnet/core/web-api/handle-errors?view=aspnetcore-8.0
  • Translating Exceptions into Problem Details Responses https://timdeschryver.dev/blog/translating-exceptions-into-problem-details-responses#
• Result Pattern https://www.milanjovanovic.tech/blog/functional-error-handling-in-dotnet-with-the-result-pattern
• IMiddleware https://www.milanjovanovic.tech/blog/3-ways-to-create-middleware-in-asp-net-core