OpenAPI Development in Arch Linux

It as been a while since i’ve engaged with C#. In this article I’ll describe a step-by-step on how to setup your Arch Linux to implement a .netcore application implementation of OpenAPI.

Instalation

Let’s start by making sure we have the SDK and runtime packages available on the system.

sudo pacman -S dotnet-runtime dotnet-sdk

We can validate the existing enviroments with the command

dotnet --list-sdks

At the time of this writing

6.0.100 [/usr/share/dotnet/sdk]

Microsoft recommends using Visual Studio Code i will skip that part but here is the url in case of need.

Hello World

Now let’s do a quick 5m Hello world just to make sure everything is working properly.

dotnet new console -o MyApp

One should have a similar output

The template "Console App" was created successfully.

Processing post-creation actions...
Running 'dotnet restore' on /home/rramos/Development/hello/MyApp/MyApp.csproj...
  Determining projects to restore...
  Restored /home/rramos/Development/hello/MyApp/MyApp.csproj (in 2.82 sec).
Restore succeeded.

Now let’s run this amazing helloworld

cd MyApp
dotnet run

One should get the desirable outcome

Hello, World!

Congratulations, you’ve built and run your .NET app. Let’s clean the space now

cd ..
rm  -rf MyApp

OpenAPI

Now let’s create our webAPI

dotnet new webapi -o WebApi1

Next lets add the Swashbuckle.AspNetCore package

dotnet add package Swashbuckle.AspNetCore

At this stage if you try to build it works but fails on the execution with the following error:

That is because Arch linux ships ASPNet in a different package. To Solve one should install the extra package using pacman.

sudo pacman -Sy aspnet-runtime

After the installation if we check the exiting runtimes

dotnet --list-runtimes

One should have the following

Microsoft.AspNetCore.App 6.0.0 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 6.0.0 [/usr/share/dotnet/shared/Microsoft.NETCore.App]

Lets try to run it now

dotnet run

You should have a similar output

Building...
info: Microsoft.Hosting.Lifetime[14]
      Now listening on: https://localhost:7177
info: Microsoft.Hosting.Lifetime[14]
      Now listening on: http://localhost:5169
info: Microsoft.Hosting.Lifetime[0]
      Application started. Press Ctrl+C to shut down.
info: Microsoft.Hosting.Lifetime[0]
      Hosting environment: Development
info: Microsoft.Hosting.Lifetime[0]
      Content root path: /home/rramos/Development/WebApi1/

Now that looks promissing let’s test the the endpoint by using the browser on

https://localhost:7177/swagger/index.html

One should see a WeatherForecast service which is the baseline service when created the project.

Leave this runnig for now and open a new terminal to create a client.

Client

Now that we have our service running let’c create a client by retrieving the OpenAPI description.

For that we will be using the NSwag.ApiDescription.Client package.

Let’s start by creating a new client project and retrieving the OpenAPI description file from swagger.

cd ..
dotnet new console -o console
cd console
mkdir openapi
wget --no-check-certificate https://localhost:7177/swagger/v1/swagger.json -O openapi/weather.json

Now lets add the required package

dotnet add package NSwag.ApiDescription.Client --version 13.15.5

If one checks the console.csproj file we can see the package was added. Although i have added a specific version is not relevant.

We are also going to need the following package

dotnet add package Newtonsoft.Json

Add the following block on the console.csproj file

<ItemGroup>
  <OpenApiReference Include="openapi/weather.json" Namespace="WeatherService">
    <ClassName>WeatherClient</ClassName>
    <OutputPath>WeatherClient.cs</OutputPath>
  </OpenApiReference>
</ItemGroup>

Now execute the build command to generate the WeatherService classes

dotnet build

You should have a similar output

Microsoft (R) Build Engine version 17.0.0+c9eb9dd64 for .NET
Copyright (C) Microsoft Corporation. All rights reserved.

  Determining projects to restore...
  All projects are up-to-date for restore.

  GenerateNSwagCSharp:
    dotnet --roll-forward-on-no-candidate-fx 2 "/home/rramos/.nuget/packages/nswag.msbuild/13.14.5/build/../tools/Net60//dotnet-nswag.dll" openapi2csclient /className:WeatherClient /namespace:WeatherService /input:"/home/rramos/Development/console/openapi/weather.json" /output:"obj/WeatherClient.cs"
  NSwag command line tool for .NET Core Net60, toolchain v13.14.5.0 (NJsonSchema v10.5.2.0 (Newtonsoft.Json v13.0.0.0))
  Visit http://NSwag.org for more information.
  NSwag bin directory: /home/rramos/.nuget/packages/nswag.msbuild/13.14.5/tools/Net60
  Code has been successfully written to file.

  Duration: 00:00:00.6921924
  console -> /home/rramos/Development/console/bin/Debug/net6.0/console.dll

Build succeeded.
    0 Warning(s)
    0 Error(s)

Time Elapsed 00:00:04.17

And a brand new WeatherClient Class is now available to use on your main Program so let’s use the following on Program.cs

// Configure HttpClientHandler to ignore certificate validation errors.
using var httpClientHandler = new HttpClientHandler();
httpClientHandler.ServerCertificateCustomValidationCallback = (message, cert, chain, errors) => { return true; };

// Create WeatherClient.
using var httpClient = new HttpClient(httpClientHandler);
var weatherClient = new WeatherService.WeatherClient("https://localhost:7177", httpClient);

// Call WeatherForecast API.
var forecast = await weatherClient.GetWeatherForecastAsync();
foreach (var item in forecast)
{
  Console.WriteLine($"{item.Date} - {item.Summary}");
}

If one runs the client now with dotnet run the following output is expected.

12/20/2021 10:34:23 PM +00:00 - Freezing
12/21/2021 10:34:23 PM +00:00 - Cool
12/22/2021 10:34:23 PM +00:00 - Hot
12/23/2021 10:34:23 PM +00:00 - Scorching
12/24/2021 10:34:23 PM +00:00 - Scorching

Hurray our client receives the API data and both client and server seems to be working
Archnt to run the service and setup a CI/CD process for it. Also to extend the service or create something more appealing.

References