Exercise - Create a web API project


This module uses the .NET 8.0 SDK. Ensure that you have .NET 8.0 installed by running the following command in your preferred command terminal:

dotnet --list-sdks

Output similar to the following example appears:

6.0.317 [C:\Program Files\dotnet\sdk]
7.0.401 [C:\Program Files\dotnet\sdk]
8.0.100 [C:\Program Files\dotnet\sdk]

Ensure that a version that starts with 8 is listed. If none is listed or the command isn't found, install the most recent .NET 8.0 SDK.

Create and explore a web API project

To set up a .NET project to work with the web API, we use Visual Studio Code. Visual Studio Code includes an integrated terminal that makes creating a new project easy. If you don't want to use a code editor, you can run the commands in this module in a terminal.

  1. In Visual Studio Code, select File > Open Folder.

  2. Create a new folder named ContosoPizza in the location of your choice, and then choose Select Folder.

  3. Open the integrated terminal from Visual Studio Code by selecting View > Terminal from the main menu.

  4. In the terminal window, copy and paste the following command:

    dotnet new webapi -controllers -f net8.0

    This command creates the files for a basic web API project that uses controllers, along with a C# project file named ContosoPizza.csproj that returns a list of weather forecasts. If you get an error, ensure that you have the .NET 8 SDK installed.


    Web API projects are secured with https by default. If you have problems, configure the ASP.NET Core HTTPS development certificate.

    You might receive a prompt from Visual Studio Code to add assets to debug the project. Select Yes in the dialog.

    The command uses an ASP.NET Core project template aliased as webapi to scaffold a C#-based web API project. A ContosoPizza directory is created. This directory contains an ASP.NET Core project running on .NET. The project name matches the ContosoPizza directory name.

    You should now have access to these files and directories:

    -| Controllers
    -| obj
    -| Properties
    -| appsettings.Development.json
    -| appsettings.json
    -| ContosoPizza.csproj
    -| ContosoPizza.http
    -| Program.cs
    -| WeatherForecast.cs
  5. Examine the following files and directories:

    Name Description
    Controllers/ Contains classes with public methods exposed as HTTP endpoints.
    Program.cs Configures services and the app's HTTP request pipeline, and contains the app's managed entry point.
    ContosoPizza.csproj Contains configuration metadata for the project.
    ContosoPizza.http Contains configuration to test REST APIs directly from Visual Studio Code.

Build and test the web API

  1. Run the following .NET Core CLI command in the command shell:

    dotnet run

    The preceding command:

    • Locates the project file at the current directory.
    • Retrieves and installs any required project dependencies for this project.
    • Compiles the project code.
    • Hosts the web API with the ASP.NET Core Kestrel web server at both an HTTP and HTTPS endpoint.

    A port from 5000 to 5300 is selected for HTTP, and from 7000 to 7300 for HTTPS, when the project is created. You can easily change the ports that you use during development by editing the project's launchSettings.json file. This module uses the secure localhost URL that begins with https.

    You should get output similar to the following, indicating that your app is running:

    info: Microsoft.Hosting.Lifetime[14]
          Now listening on: https://localhost:7294
    info: Microsoft.Hosting.Lifetime[14]
          Now listening on: http://localhost:5118 
    info: Microsoft.Hosting.Lifetime[0]
          Application started. Press Ctrl+C to shut down.
    info: Microsoft.Hosting.Lifetime[0]
          Hosting environment: Development        

    If you're running this app on your own machine, you could direct a browser to the HTTPS link displayed in the output (in the preceding case, https://localhost:7294) to view the resulting page. Remember this port, because you use it throughout the module where {PORT} is used.


    Check the terminal output if you encounter any unexpected behavior. If the build fails or other errors occur, the log file's information helps you troubleshoot. As you make changes to the code, you'll need to stop the web API by selecting CTRL+C on the keyboard and rerunning the dotnet run command.

  2. Open a web browser and go to:


    You should see JSON output similar to this example:

        "date": "2021-11-09T20:36:01.4678814+00:00",
        "temperatureC": 33,
        "temperatureF": 91,
        "summary": "Scorching"
        "date": "2021-11-09T20:36:01.4682337+00:00",
        "temperatureC": -8,
        "temperatureF": 18,
        "summary": "Cool"
        // ...

Optional: Explore with .http files

Included in the project is ContosoPizza.http, a file that is used to test API endpoints through a standard format. .http files are supported in several Integrated development environments (IDEs) including Visual Studio and inside of Visual Studio Code with the REST Client extension installed.

  1. Open the ContosoPizza.http file.

    In some IDEs, this file is preconfigured with the @ContosoPizza_HostAddress variables and a GET command calling /weatherforecast/ that accepts application/json.

  2. If it's present in your file, select the Sent Request command above the GET which sends a request to the running service.

    Calling this command opens a response window with output similar to what we saw in the browser:

    HTTP/1.1 200 OK
    Connection: close
    Content-Type: application/json; charset=utf-8
    Date: Wed, 17 Jan 2024 16:46:40 GMT
    Server: Kestrel
    Transfer-Encoding: chunked
            "date": "2024-01-18",
            "temperatureC": -2,
            "temperatureF": 29,
            "summary": "Warm"
            "date": "2024-01-19",
            "temperatureC": 24,
            "temperatureF": 75,
            "summary": "Chilly"
        // ..

Optional: Explore APIs with Command Line HTTP REPL

  1. Open a new integrated terminal from Visual Studio Code by selecting Terminal > New Terminal from the main menu, then run the following command:

    dotnet tool install -g Microsoft.dotnet-httprepl

    The preceding command installs the .NET HTTP REPL command-line tool that you use to make HTTP requests to the web API.

  2. Connect to the web API by running the following command:

    httprepl https://localhost:{PORT}

    Alternatively, run the following command at any time while HttpRepl is running:

    connect https://localhost:{PORT}


    If the HttpRepl tool warns Unable to find an OpenAPI description, the most likely cause is an untrusted development certificate. HttpRepl requires a trusted connection. Before you can continue, you must configure your system to trust the dev certificate with dotnet dev-certs https --trust

  3. Explore available endpoints by running the following command:


    The preceding command detects all APIs available on the connected endpoint and lists them, as in the following output:

    https://localhost:{PORT}/> ls
    .                 []
    WeatherForecast   [GET] 
  4. Go to the WeatherForecast endpoint by running the following command:

    cd WeatherForecast

    The preceding command shows an output of available APIs for the WeatherForecast endpoint:

    https://localhost:{PORT}/> cd WeatherForecast
    /WeatherForecast    [GET]
  5. Make a GET request in HttpRepl by using the following command:


    The preceding command makes a GET request similar to going to the endpoint in the browser:

    HTTP/1.1 200 OK
    Content-Type: application/json; charset=utf-8
    Date: Fri, 02 Apr 2021 17:31:43 GMT
    Server: Kestrel
    Transfer-Encoding: chunked
        "date": 4/3/2021 10:31:44 AM,
        "temperatureC": 13,
        "temperatureF": 55,
        "summary": "Sweltering"
        "date": 4/4/2021 10:31:44 AM,
        "temperatureC": -13,
        "temperatureF": 9,
        "summary": "Warm"
        // ..
  6. End the current HttpRepl session by using the following command:

  7. Return to the dotnet terminal in the drop-down list in Visual Studio Code. Shut down the web API by selecting CTRL+C on your keyboard.

Now that you created the web API, we can modify it to meet the needs of the pizza web API.