Swagger UI and OpenAPI in Dotnet 9

Detailed Documentation: Using OpenApi Documents

Install NuGet Package: Swashbuckle.AspNetCore.SwaggerUI

// add OpenApi document generation
builder.Services.AddOpenApi();
 
var app = builder.Build();
 
// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
		// enable the OpenApi document endpoint
    app.MapOpenApi();
    
    // enable Swagger UI based on the OpenApi document
    app.UseSwaggerUI(options =>
    {
        options.SwaggerEndpoint("/openapi/v1.json", "v1");
    });
}