How To Upgrade ASP.NET Core 2.1 To ASP.NET Core 3.1 version

Additionally, If you have implemented SignalR then you will get information or warning messages like this :

In ASP.NET Core 2.1 application, SignalR is written as shown below which resides inside the Configuration() method of Startup.cs file.

app.UseSignalR(routes => {
    routes.MapHub < ChatUpdaterHub > ("/chat-updater");
});

However, in ASP.NET Core 3.1 it should be implemented with endpoints as illustrated in the below code.

app.UseEndpoints(endpoints => {
    endpoints.MapHub < ChatUpdaterHub > ("/chat-updater"); //Signal R implementation
    endpoints.MapControllerRoute(name: "default", pattern: "{controller=Home}/{action=Index}/{id?}");
});

Code of Startup.cs class of .NET Core 2.1 is

public class Startup {
    public IConfiguration Configuration {
        get;
    }
    public Startup(IConfiguration configuration) {
        this.Configuration = configuration;
    }
    public void ConfigureServices(IServiceCollection services) {
        services.AddSingleton(defaultEndpointsSettings);
        services.AddDistributedMemoryCache();
        services.AddTransient < ApiRequester > ();
        services.AddHostedService < FetchingBackgroundService > ();
        services.AddMvc();
        services.AddSignalR();
    }
    public void Configure(IApplicationBuilder app, IHostingEnvironment env) {
        if (env.IsDevelopment()) {
            app.UseDeveloperExceptionPage();
        } else {
            app.UseExceptionHandler("/Home/Error");
        }
        var cachePeriod = env.IsDevelopment() ? "600" : "604800";
        app.UseStaticFiles(new StaticFileOptions {
            OnPrepareResponse = ctx => {
                ctx.Context.Response.Headers.Append("Cache-Control", $ "public, max-age={cachePeriod}");
            }
        });
        app.UseSignalR(routes => {
            routes.MapHub < DataUpdaterHub > ("/ws-updater");
        });
        app.UseMvc(routes => {
            routes.MapRoute(name: "default", template: "{controller=Home}/{action=Index}/{id?}");
        });
    }
}

When we upgrade the same project to .Net Core 3.1 Startup.cs class should be like this,

 public class Startup
    {
        public IConfiguration Configuration { get; }
        public IWebHostEnvironment Environment { get; }
        public Startup(IConfiguration configuration, IWebHostEnvironment environment)
        {
            this.Configuration = configuration;
            Environment = environment;
        }

        public void ConfigureServices(IServiceCollection services)
        {            
           
            services.AddSingleton(defaultEndpointsSettings);
            services.AddDistributedMemoryCache();
            services.AddTransient<ApiRequester>();
            services.AddHostedService<FetchingBackgroundService>();
            services.AddMvc();
            services.AddSignalR();
           
        }

        public void Configure(IApplicationBuilder app)
        {
            if (Environment.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Home/Error");
            }

            var cachePeriod = Environment.IsDevelopment() ? "600" : "604800";
            app.UseStaticFiles(new StaticFileOptions
            {
                OnPrepareResponse = ctx =>
                {
                    ctx.Context.Response.Headers.Append("Cache-Control", $"public, max-age={cachePeriod}");
                }
            });            
            app.UseRouting();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapHub<DataUpdaterHub>("/ws-updater");
                endpoints.MapControllerRoute(
                    name: "default",
                    pattern: "{controller=Home}/{action=Index}/{id?}");
            });
        }
    }

Microsoft Recommendation

Microsoft’s recommendation for migration to .NET Core 3.1 is:

• Add UseRouting()
• Sequence of UseStatisFiles(), UseRouting(), UseAuthentication() and UseAuthorization(), UseCors() and UseEndPoints() should be in following order

Conclusion

This article described the guidelines to upgrade the .NET Core from 2.1 (or lower versions) to 3.1 with sample code and examples of errors and how to resolve them. I hope it will help you to update your application from lower framework to upper with long-term support.