Startup.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Microsoft.OpenApi.Models;

namespace VersioningSwagger_Sample
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllers();
            services.AddApiVersioning();
            services.AddVersionedApiExplorer(x =>
            {
                // add the versioned api explorer, which also adds IApiVersionDescriptionProvider service
                // note: the specified format code will format the version as "'v'major[.minor][-status]"
                x.GroupNameFormat = "'v'VVV";

                // note: this option is only necessary when versioning by url segment. the SubstitutionFormat
                // can also be used to control the format of the API version in route templates
                x.SubstituteApiVersionInUrl = true;
            });
            services.AddSwaggerGen(c =>
            {
                c.SwaggerDoc("v1", new OpenApiInfo { Title = "VersioningSwagger_Sample", Version = "v1" });
                c.SwaggerDoc("v2", new OpenApiInfo { Title = "VersioningSwagger_Sample", Version = "v2" });
            });
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
                app.UseSwagger();
                app.UseSwaggerUI(c =>
                {
                    c.SwaggerEndpoint("/swagger/v1/swagger.json", "VersioningSwagger_Sample v1");
                    c.SwaggerEndpoint("/swagger/v2/swagger.json", "VersioningSwagger_Sample v2");
                });
            }

            app.UseHttpsRedirection();

            app.UseRouting();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });
        }
    }
}