Configure

In an ASP.NET Core Web Application, we must set up Endpoints in the Configure method. When a visitor goes to the website, endpoints are then used.

Getting started

Please create a new ASP.NET Core Web Application in Visual Studio, and specify that it is Empty to start. We will then open the Startup class.

Configure example

In Configure, you will see some generated code such as a UseRouting and UseEndpoints call. These should be left in place.

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Hosting;

namespace WebApplication3
{
    public class Startup
    {
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseRouting();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapGet("/", async context =>
                {
                    await context.Response.WriteAsync(GetHitCount());
                });
            });
        }

        int _hits;

        string GetHitCount()
        {
            // Increment hit count field.
            // ... Return string that indicates hit count.
            return $"Hit count: {++_hits}";
        }
    }
}
Hit count: 1

Notes, UseRouting

It is important that we leave the UseRouting call in place when we call UseEndpoints in Configure. We get an InvalidOperationException otherwise.

System.InvalidOperationException
EndpointRoutingMiddleware matches endpoints setup by EndpointMiddleware
and so must be added to the request execution pipeline before EndpointMiddleware.
Please add EndpointRoutingMiddleware by calling 'IApplicationBuilder.UseRouting'
inside the call to 'Configure(...)' in the application startup code.

UseStaticFiles

We can call the UseStaticFiles method in Configure as well. We must add a "wwwroot" directory to store the static files for public access.

Summary

By specifying a method call in the MapGet lambda, we can execute code from the Configure method in ASP.NET Core. We can use this to begin developing a web application.