Using 'UseMvc' to configure MVC is not supported while using Endpoint Routing

I had an Asp.Net core 2.2 project.

Recently, I changed the version from .net core 2.2 to .net core 3.0 Preview 8. After this change I see this warning message:

> using 'UseMvc' to configure MVC is not supported while using Endpoint > Routing. To continue using 'UseMvc', please set > 'MvcOptions.EnableEndpointRouting = false' inside 'ConfigureServices'.

I understand that by setting EnableEndpointRouting to false I can solve the issue, but I need to know what is the proper way to solve it and why Endpoint Routing does not need UseMvc() function.

I found the solution, in the following official documentation "Migrate from ASP.NET Core 2.2 to 3.0":

There are 3 approaches: > 1. Replace UseMvc or UseSignalR with UseEndpoints.

In my case, the result looked like that

  public class Startup
{
    
    public void ConfigureServices(IServiceCollection services)
    {
        //Old Way
        services.AddMvc();
        // New Ways
        //services.AddRazorPages();
    }

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

        app.UseStaticFiles();
        app.UseRouting();
        app.UseCors();

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

> OR
> 2. Use AddControllers() and UseEndpoints()

public class Startup
{
    
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddControllers();
    }

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

        app.UseStaticFiles();
        app.UseRouting();
        app.UseCors();

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

> OR
> 3. Disable endpoint Routing. As the exception message suggests and as mentioned in the following section of documentation: use mvcwithout endpoint routing

services.AddMvc(options => options.EnableEndpointRouting = false);
//OR
services.AddControllers(options => options.EnableEndpointRouting = false);

This worked for me (add in Startup.cs > ConfigureServices method):

services.AddMvc(option => option.EnableEndpointRouting = false)

> but I need to know what is the proper way to solve it

In general, you should use EnableEndpointRouting instead of UseMvc, and you could refer Update routing startup code for detail steps to enable EnableEndpointRouting.

> why Endpoint Routing does not need UseMvc() function.

For UseMvc, it uses the IRouter-based logic and EnableEndpointRouting uses endpoint-based logic. They are following different logic which could be found below:

if (options.Value.EnableEndpointRouting)
{
    var mvcEndpointDataSource = app.ApplicationServices
        .GetRequiredService<IEnumerable<EndpointDataSource>>()
        .OfType<MvcEndpointDataSource>()
        .First();
    var parameterPolicyFactory = app.ApplicationServices
        .GetRequiredService<ParameterPolicyFactory>();

    var endpointRouteBuilder = new EndpointRouteBuilder(app);

    configureRoutes(endpointRouteBuilder);

    foreach (var router in endpointRouteBuilder.Routes)
    {
        // Only accept Microsoft.AspNetCore.Routing.Route when converting to endpoint
        // Sub-types could have additional customization that we can't knowingly convert
        if (router is Route route && router.GetType() == typeof(Route))
        {
            var endpointInfo = new MvcEndpointInfo(
                route.Name,
                route.RouteTemplate,
                route.Defaults,
                route.Constraints.ToDictionary(kvp => kvp.Key, kvp => (object)kvp.Value),
                route.DataTokens,
                parameterPolicyFactory);

            mvcEndpointDataSource.ConventionalEndpointInfos.Add(endpointInfo);
        }
        else
        {
            throw new InvalidOperationException($"Cannot use '{router.GetType().FullName}' with Endpoint Routing.");
        }
    }

    if (!app.Properties.TryGetValue(EndpointRoutingRegisteredKey, out _))
    {
        // Matching middleware has not been registered yet
        // For back-compat register middleware so an endpoint is matched and then immediately used
        app.UseEndpointRouting();
    }

    return app.UseEndpoint();
}
else
{
    var routes = new RouteBuilder(app)
    {
        DefaultHandler = app.ApplicationServices.GetRequiredService<MvcRouteHandler>(),
    };

    configureRoutes(routes);

    routes.Routes.Insert(0, AttributeRouting.CreateAttributeMegaRoute(app.ApplicationServices));

    return app.UseRouter(routes.Build());
}

For EnableEndpointRouting, it uses EndpointMiddleware to route the request to the endpoints.

The issue I found to be due to updates on the .NET Core framework. The latest .NET Core 3.0 released version requires explicit opt-in for using MVC.

This issue is most visible when one tries to migrate from older .NET Core(2.2 or preview 3.0 version) to .NET Core 3.0

If migrating from 2.2 to 3.0, please use the below code to fix the issue.

services.AddMvc(options => options.EnableEndpointRouting = false);

If using .NET Core 3.0 template,

services.AddControllers(options => options.EnableEndpointRouting = false);

ConfigServices method after fix as below,

Thank You

Endpoint Routing is disabled by default on ASP.NET 5.0

Just configure as in Startup

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddMvc(options => options.EnableEndpointRouting = false);
    }
    

This worked for me

You can use : in ConfigureServices method:

services.AddControllersWithViews();

And for Configure method:

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

For DotNet Core 3.1

Use below

File : Startup.cs

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{         

    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }
       
    app.UseHttpsRedirection();
    app.UseRouting();
    app.UseAuthentication();
    app.UseHttpsRedirection();
    app.UseEndpoints(endpoints =>
    {
        endpoints.MapControllers();
    });
}

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        //Old Way
        services.AddMvc();
        // New Ways
        //services.AddRazorPages();
    }

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

        app.UseStaticFiles();
        app.UseRouting();
        app.UseCors();

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

This works also in .Net Core 5

-> In ConfigureServices method - Startup.cs

        //*****REGISTER Routing Service*****
        services.AddMvc();
        services.AddControllers(options => options.EnableEndpointRouting = false);

-> In Configure Method - Startup.cs

       //*****USE Routing***** 
        app.UseMvc(Route =>{
            Route.MapRoute(
                name:"default",
                template: "{Controller=Name}/{action=Name}/{id?}"
            );
        });

This worked for me

 services.AddMvc(options => options.EnableEndpointRouting = false); or 
 OR
 services.AddControllers(options => options.EnableEndpointRouting = false);

Use Below Code

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