Add Swagger to .NET Minimal APIs (So You Can Test Endpoints in the Browser)

If you want your API to feel professional, add OpenAPI (Swagger). It gives you:

• interactive docs

• “Try it out” buttons

• request/response examples

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Step 1 — Install Swagger package

In your project folder:

dotnet add package Swashbuckle.AspNetCore

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Step 2 — Update Program.cs

Add these lines near the top:

builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

Then enable Swagger in the app pipeline before mapping endpoints:

if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

Optional: make endpoints show better names in Swagger:

group.MapGet("/", (TodoService service) => Results.Ok(service.GetAll()))
     .WithName("ListTodos")
     .WithSummary("List all todos");

group.MapPost("/", (TodoCreateDto dto, TodoService service) => { ... })
     .WithName("CreateTodo")
     .WithSummary("Create a new todo");

If your .WithSummary(...) doesn’t compile, remove it and keep .WithName(...) (your .NET SDK might require different packages/versions). The core idea still works.

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Step 3 — Run and open Swagger UI

Run:

dotnet run

Open:

/swagger

Now you can test:

• POST todo with JSON body

• GET list

• PUT update

• DELETE

External link:

• Swagger / OpenAPI concept: https://swagger.io/specification/