How to use OpenAPI in ASP.NET Core

shutterstock 1850095465 internet API application programming interface

ASP.Internet Main 6 released a simplified hosting model that allows us to make light-weight APIs with negligible dependencies. These small API jobs make it simple to get our software up and operating rapid, by composing considerably less boilerplate code. ASP.Web Main 7 even more enhanced negligible APIs by adding help for filters.

Each time you get the job done with APIs—including minimum APIs—you will frequently want to document your endpoints. The good news is, ASP.Web Main presents built-in assistance for the OpenAPI specification, so you can acquire advantage of OpenAPI and the Swagger UI to create good documentation for all of your APIs.

The aim of this article is to give you a head get started on performing so. To use the code examples supplied in this article, you should really have Visible Studio 2022 put in in your program. If you don’t previously have a copy, you can down load Visible Studio 2022 listed here.

Create a small Website API venture in Visual Studio 2022

Initial off, let’s generate an ASP.Net Main job in Visual Studio 2022. Observe these measures:

  1. Launch the Visible Studio 2022 IDE.
  2. Click on “Create new task.”
  3. In the “Create new project” window, pick out “ASP.Internet Main Internet API” from the checklist of templates exhibited.
  4. Simply click Subsequent.
  5. In the “Configure your new project” window, specify the name and site for the new task.
  6. Optionally check the “Place option and project in the similar directory” examine box, dependent on your preferences.
  7. Click on Following.
  8. In the “Additional Information” window revealed upcoming, uncheck the check out box that states “Use controllers…” because we’ll be working with minimal APIs in this illustration. Go away the “Authentication Type” established as “None” (default). Check the “Configure for HTTPS” and “Enable Open API Support” examine packing containers. Lastly, guarantee that the “Enable Docker” examine box is unchecked as we will not be using Docker here. (See Determine 1 underneath.)
  9. Simply click Build.
openapi aspnet core 01 IDG

Figure 1. Check out the Configure for HTTP and Allow OpenAPI Guidance examine packing containers. Go away Authentication set to None and the other check out boxes unchecked.

We’ll use this ASP.Net Main 7 World-wide-web API project to use OpenAPI to document negligible API endpoints in the sections under.

What is the OpenAPI specification?

Previously recognised as the Swagger specification, the OpenAPI specification defines a standard, machine-readable, programming language-agnostic interface description language (IDL) for APIs. It is a language-impartial conventional for describing HTTP APIs. The normal is supported by a combination of created-in APIs and open-supply libraries.

The three most substantial features of OpenAPI integration in an software are:

  1. Creating information and facts about the app’s endpoints.
  2. Placing the facts together in a structure appropriate with the OpenAPI typical.
  3. Exposing the produced OpenAPI schema by way of a graphical person interface or a serialized file.

Mainly because we enabled OpenAPI assist when we made our ASP.Net Core 7 Website API project, the Swashbuckle.AspNetCore deal will be extra to the undertaking immediately. Swashbuckle is an open up resource job that enables the generation of Swagger documentation.

Note that you can always add the Swashbuckle.AspNetCore NuGet deal to your other tasks manually.

Develop a uncomplicated minimal API endpoint in ASP.Web Main

When you create a new ASP.Net Core Website API task in Visible Studio, the default controller (named WeatherForecast) and product course will be produced routinely. Due to the fact we’re working with negligible APIs listed here, these files will not be established.

As an alternative, a default HTTP GET endpoint will be made in the Method.cs file. Now, swap the default produced code of the HTTP GET endpoint with the following code.

application.MapGet("", () => "Hello there Earth!")

When you operate the software, you’ll be equipped to see the Swagger UI in your world-wide-web browser, as shown in Figure 2.

openapi aspnet core 02 IDG

Figure 2. The Swagger UI.

Configure Swagger in a negligible API in ASP.Internet Main

The code snippet underneath illustrates how you can configure the Swagger middleware to increase metadata for the API doc.

builder.Providers.AddSwaggerGen(setup => setup.SwaggerDoc("v1", new OpenApiInfo()

    Description = "This is a uncomplicated implementation of a Nominal Api in Asp.Internet 7 Main",
    Title = "Demo Api",
    Model = "v1",
    Get in touch with = new OpenApiContact()
        Title = "Joydip Kanjilal",
        Url = new Uri("")

When you execute the software now, the metadata you additional will be exhibited in the Swagger UI as revealed in Determine 3.

openapi aspnet core 03 IDG

Figure 3. Including API metadata.

Make a design course

Now let us flesh out our minimum API case in point application. Initially, make a product class using the subsequent code.

community course Author

    community int Id  get established 
    community string FirstName  get established 
    general public string LastName  get set 
    public string Handle  get established 
    public string E mail  get established 
    public string Cellphone  get set 

Produce and carry out an interface

Up coming, develop an interface named IAuthorRepository and enter the subsequent code.

public interface IAuthorRepository

    Creator GetById(int id)
    void Generate(Author entity)
    void Delete(Writer entity)
    void Update(Author entity)

Now build an additional class named AuthorRepository and enter the adhering to code.

public course AuthorRepository : IAuthorRepository

    void IAuthorRepository.Produce(Writer entity)
        throw new NotImplementedException()
    void IAuthorRepository.Delete(Creator entity)
        throw new NotImplementedException()
    Creator IAuthorRepository.GetById(int id)
        throw new NotImplementedException()
    void IAuthorRepository.Update(Author entity)
        toss new NotImplementedException()

Notice that none of the approaches of the AuthorRepository class have been carried out.  We’ll use this skeleton implementation just for the uses of viewing how we can work with OpenAPI in minimum API programs.

Create a nominal API endpoint

Finally, delete the endpoint we established before given that we won’t be needing it any longer. Rather, insert the subsequent piece of code to your Software.cs file to produce 4 new endpoints.

app.MapGet("/authors/id", async ([FromServices] Author entity, int id) =>

    return Benefits.Alright()
application.MapPost("/authors", async ([FromServices] Author entity) =>

    return Effects.Okay()
app.MapPut("/authors/id", async ([FromServices] int id, Creator entityToUpdate) =>

    return Effects.Alright()
app.MapDelete("/authors/id", async ([FromServices] int id) =>

    return Benefits.Ok()

When you run the software, you really should see these endpoints shown in your Swagger UI as in Determine 4.

openapi aspnet core 04 IDG

Figure 4. The four endpoints of our nominal API.

Finish negligible API instance in ASP.Net Core

The full code listing for our OpenAPI-documented small API is specified beneath for your reference.

working with Microsoft.AspNetCore.Mvc
applying Microsoft.OpenApi.Designs
var builder = WebApplication.CreateBuilder(args)
// Add companies to the container.
builder.Products and services.AddEndpointsApiExplorer()
builder.Providers.AddSwaggerGen(set up => setup.SwaggerDoc("v1", new OpenApiInfo()

    Description = "This is a very simple implementation of a Negligible Api in Asp.Internet 7 Main",
    Title = "Demo Api",
    Version = "v1",
    Get hold of = new OpenApiContact()
        Name = "Joydip Kanjilal",
        Url = new Uri("")
var application = builder.Make()
// Configure the HTTP request pipeline.
if (application.Ecosystem.IsDevelopment())


app.MapGet("/authors/id", async ([FromServices] Author entity, int id) =>

    return Effects.Alright()
application.MapPost("/authors", async ([FromServices] Writer entity) =>

    return Results.Ok()
app.MapPut("/authors/id", async ([FromServices] int id, Writer entityToUpdate) =>

    return Benefits.Okay()
application.MapDelete("/authors/id", async ([FromServices] int id) =>

    return Results.Ok()
community course Writer

    community int Id  get set 
    community string FirstName  get established 
    public string LastName  get established 
    community string Handle  get set 
    community string Email  get set 
    community string Cellphone  get established 

general public interface IAuthorRepository

    Author GetById(int id)
    void Build(Writer entity)
    void Delete(Writer entity)
    void Update(Author entity)

public course AuthorRepository : IAuthorRepository

    void IAuthorRepository.Make(Writer entity)
        toss new NotImplementedException()
    void IAuthorRepository.Delete(Creator entity)
        throw new NotImplementedException()
    Writer IAuthorRepository.GetById(int id)
        throw new NotImplementedException()
    void IAuthorRepository.Update(Author entity)
        toss new NotImplementedException()

By enabling OpenAPI guidance in your Internet API assignments when you generate them, you can have ASP.Net Core mechanically doc your HTTP endpoints, and you can look at that information and facts as a result of the Swagger UI. Observe you can customise the Swagger UI using Cascading Type Sheets, display enum values as string values, and develop different Swagger paperwork for distinctive versions of your API.

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