Let's perform the following steps:

1. Create a new folder called Middleware within your project, and then add a new class called CommunicationMiddleware.cs, with the following code:

        using Microsoft.AspNetCore.Http;
        using TicTacToe.Services;
        public class CommunicationMiddleware 
        { 
          private readonly RequestDelegate _next; 
          private readonly IUserService _userService; 
 
          public CommunicationMiddleware(RequestDelegate next,
           IUserService userService) 
          { 
            _next = next; 
            _userService = userService; 
          }  
          public async Task Invoke(HttpContext context) 
          { 
            await _next.Invoke(context); 
          } 
        }

2. Create a new folder called Extensions within your project, and then add a new class called CommunicationMiddlewareExtension.cs, with the following code:

       using Microsoft.AspNetCore.Builder;
       using TicTacToe.Middleware;        
        
        public static class CommunicationMiddlewareExtension 
        { 
          public static IApplicationBuilder
           UseCommunicationMiddleware(this IApplicationBuilder app) 
          { 
            return app.UseMiddleware<CommunicationMiddleware>(); 
          } 
        } 

3. Add a using directive for TicTacToe.Extensions in the Startup class, and then add the communication middleware to the Configure method:

        using TicTacToe.Extensions; 
        ... 
        public void Configure(IApplicationBuilder app,
         IHostingEnvironment env) 
        { 
          ... 
          app.UseCommunicationMiddleware();
          app.UseRouting();            
          app.UseEndpoints(endpoints =>
          {
              endpoints.MapControllerRoute(
                  name: "default",
                  pattern: "{controller=Home}/{action=Index}
                  /{id?}");
              endpoints.MapRazorPages();
            });          
        } 

4. Set some breakpoints in the communication middleware implementation and start the application by pressing F5. You will see that the breakpoints will be hit if everything is working correctly:

This is just a basic example of how to create your own middleware; there are no functional changes visible between this section and the others. You are going to further implement the various functionalities for finalizing the Tic-Tac-Toe application in the next chapters, and the communication middleware seen in this chapter is going to do some real work shortly.