What is Swagger and how do you use it to document a .NET Core Web API?

Swagger is an open-source tool for documenting RESTful APIs. It provides a user-friendly interface that allows developers to visualize and interact with the API resources and methods. Swagger also provides a way to automatically generate client libraries for various programming languages, making it easier to consume the API.

To use Swagger to document a .NET Core Web API, you can follow these steps:Install the Swashbuckle NuGet package in your project.
Configure the Swagger middleware in your application startup code.
Add Swagger documentation to your controllers and methods using attributes like [SwaggerOperation] and [SwaggerResponse].
Run your application and navigate to the Swagger UI page to view and interact with your API documentation.

Here is an example of how you can configure Swagger in your startup code:

using Microsoft.OpenApi.Models;
using Swashbuckle.AspNetCore.SwaggerGen;
using Swashbuckle.AspNetCore.SwaggerUI;

// ...

public void ConfigureServices(IServiceCollection services)
{
    // ...

    services.AddSwaggerGen(options =>
    {
        options.SwaggerDoc("v1", new OpenApiInfo
        {
            Title = "My API",
            Version = "v1",
            Description = "My awesome API documentation"
        });
    });

    // ...
}

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    // ...

    app.UseSwagger();
    app.UseSwaggerUI(options =>
    {
        options.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1");
        options.RoutePrefix = string.Empty;
    });

    // ...
}

In this example, we are configuring Swagger to generate documentation for our API with version v1. We also specify the API title, version, and description. Finally, we add middleware to serve the Swagger UI page, which can be accessed at the root URL of our application (/).