dotnet-core/release-notes/3.0/preview/api-diff/preview9/Asp.Net/3.0-preview9_Microsoft.AspNetCore.Mvc.md

Microsoft.AspNetCore.Mvc

 namespace Microsoft.AspNetCore.Mvc {
     public abstract class ControllerBase {
+        public ProblemDetailsFactory ProblemDetailsFactory { get; set; }
+        public virtual ObjectResult Problem(string detail = null, string instance = null, Nullable<int> statusCode = default(Nullable<int>), string title = null, string type = null);
+        public virtual ActionResult ValidationProblem(string detail = null, string instance = null, Nullable<int> statusCode = default(Nullable<int>), string title = null, string type = null, ModelStateDictionary modelStateDictionary = null);
     }
 }