Viewresultexecutor changes in ASP. NET Core 2.1

Code that previously worked correctly in ASP. NET Core 2.0:

varServices =httpcontext.requestservices;varExecutor = Services. Getrequiredservice<viewresultexecutor>();varViewengine = Services. Getrequiredservice<irazorviewengine>();varView = Viewengine.getview (NULL,"~/pages/iealert.cshtml",true)?. View;if(View! =NULL){    using(View asIDisposable) {        awaitExecutor. Executeasync (ControllerContext, view, ViewData, TempData,"text/html; Charset=utf-8", $); }    return NewEmptyresult ();} 

The following error occurred after upgrading to ASP. NET Core 2.1:

System.InvalidOperationException:No Service for type ' Microsoft.AspNetCore.Mvc.ViewFeatures.ViewResultExecutor ' have been registered.   At Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService ( IServiceProvider provider, Type servicetype) at   Microsoft.extensions.dependencyinjection.serviceproviderserviceextensions.getrequiredservice[t] ( IServiceProvider provider)

View the definition of Viewresultexecutor discovery Viewresultexecutor implements the Iactionresultexecutor<viewresult> interface to view the latest source generation of ASP. Code to find such registrations:

Services. Tryaddsingleton<iactionresultexecutor<viewresult>, viewresultexecutor> ();

The original viewresultexecutor was also abstracted, so instead of the following code to solve the problem:

varServices =httpcontext.requestservices;varExecutor = Services. Getrequiredservice<iactionresultexecutor<viewresult>> () asViewresultexecutor??Throw NewArgumentNullException ("Executor");varViewengine = Services. Getrequiredservice<irazorviewengine>();varView = Viewengine.getview (NULL,"~/pages/iealert.cshtml",true)?. View;if(View! =NULL){    using(View asIDisposable) {        awaitExecutor. Executeasync (ControllerContext, view, ViewData, TempData,"text/html; Charset=utf-8", $); }    return NewEmptyresult ();}

Viewresultexecutor changes in ASP. NET Core 2.1