Resolved - Error While Upgrading Solution From ASP.NET Core 2.1 To ASP.NET Core 3.1

In this blog, you will learn how to resolve the error while upgrading solution from ASP.NET Core 2.1 to ASP.NET Core 3.1.

I was upgrading the project framework from ASP.NET Core 2.1 to ASP.NET Core 3.1 and I got the below exception error in my Startup.cs class.

Error Details

“System.InvalidOperationException HResult=0x80131509 Message=Endpoint Routing does not support ‘IApplicationBuilder.UseMvc(…)’. 
To use ‘IApplicationBuilder.UseMvc’ set ‘MvcOptions.EnableEndpointRouting = false’ inside ‘ConfigureServices(…). Source=Microsoft.AspNetCore.Mvc.Core StackTrace: at 
Microsoft.AspNetCore.Builder.MvcApplicationBuilderExtensions.UseMvc(IApplicationBuilder app, 
Action`1 configureRoutes) at ProjectName.Startup.Configure(IApplicationBuilder app, 
IHostingEnvironment env) in ProjectDirectoryPath\Startup.cs:line 89 at 
System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean 
constructor, Boolean wrapExceptions) at System.Reflection.RuntimeMethodInfo.Invoke(Object obj,
 BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) at 
Microsoft.AspNetCore.Hosting.ConfigureBuilder.Invoke(Object instance, IApplicationBuilder builder) 
at Microsoft.AspNetCore.Hosting.ConfigureBuilder.<>c__DisplayClass4_0.
<Build>b__0(IApplicationBuilder builder) at 
Microsoft.AspNetCore.Hosting.ConventionBasedStartup.Configure(IApplicationBuilder app)”

When I continued to run the project, the page loaded with the below error message.

Solution

Inside Configuration() method of Startup.cs file, we need to change the below code.

app.UseMvc(routes => {
    routes.MapRoute(name: "default", template: "{controller=Home}/{action=Index}/{id?}");
});

To

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

The thing is after migration to ASP.NET Core 3.1, we have to use UseEndPoints() instead of UseMVC().

I hope this helps you resolve your issue after upgrading your project framework from ASP.NET Core 2.1 to ASP.NET Core 3.1.