Add IsApiVersionNeutral only if not defined ApiVersionAttribute.

src/Volo.Abp.AspNetCore.Mvc/Microsoft/Extensions/DependencyInjection/AbpApiVersioningOptionsExtensions.cs

@@ -1,5 +1,6 @@
 using System.Linq;
 using System.Reflection;
+using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.Mvc.Versioning;
 using Microsoft.AspNetCore.Mvc.Versioning.Conventions;
 using Volo.Abp.AspNetCore.Mvc;
@@ -53,10 +54,13 @@ namespace Microsoft.Extensions.DependencyInjection
                 }
                 else
                 {
-                    typeof(ControllerApiVersionConventionBuilder<>)
+                    if (!controllerType.IsDefined(typeof(ApiVersionAttribute), true))
-                        .MakeGenericType(controllerType)
+                    {
-                        .GetMethod("IsApiVersionNeutral")
+                        typeof(ControllerApiVersionConventionBuilder<>)
-                        .Invoke(controllerBuilder, null);
+                            .MakeGenericType(controllerType)
+                            .GetMethod("IsApiVersionNeutral")
+                            .Invoke(controllerBuilder, null);
+                    }
                 }
             }
         }

src/Volo.Abp.Identity.HttpApi/Volo/Abp/Identity/FixtureController.cs

@@ -10,22 +10,22 @@ namespace Volo.Abp.Identity
     [Route("api/v{api-version:apiVersion}/identity/fixture")]
     public class FixtureController : AbpController, IRemoteService
     {
-        [HttpGet]
+        [HttpGet, MapToApiVersion("2.0")]
         public int Get()
         {
-            return 42;
+            return 41;
         }
 
-        //[HttpGet, MapToApiVersion("3.0")]
+        [HttpGet, MapToApiVersion("3.0")]
-        //public int Get3()
+        public int Get3()
-        //{
+        {
-        //    return 42;
+            return 42;
-        //}
+        }
 
         [HttpPost]
         public int Post()
         {
-            return 42;
+            return 43;
         }
     }
 }