之前在 ASP.NET Core 2.0 中可以正常运行的代码：
var services = HttpContext.RequestServices;var executor = services.GetRequiredService<ViewResultExecutor>();var viewEngine = services.GetRequiredService<IRazorViewEngine>();var view = viewEngine.GetView(null, "~/Pages/IeAlert.cshtml", true)?.View;if (view != null){ ???using (view as IDisposable) ???{ ???????await executor.ExecuteAsync(ControllerContext, view, ViewData, TempData, "text/html; charset=utf-8", 200); ???} ???return new EmptyResult();} 升级到 ASP.NET Core 2.1 之后出现下面的错误：
System.InvalidOperationException: No service for type ‘Microsoft.AspNetCore.Mvc.ViewFeatures.ViewResultExecutor‘ has been registered. ??at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType) ??at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService[T](IServiceProvider provider)
查看 ViewResultExecutor 的定义发现 ViewResultExecutor 实现了 IActionResultExecutor<ViewResult> 接口，查看最新的 ASP.NET Core MVC 的源代码发现这样的注册：
services.TryAddSingleton<IActionResultExecutor<ViewResult>, ViewResultExecutor>();
原来 ViewResultExecutor 也被抽象了，于是改为下面的代码解决了问题：
var services = HttpContext.RequestServices;var executor = services.GetRequiredService<IActionResultExecutor<ViewResult>>() as ViewResultExecutor ????? throw new ArgumentNullException("executor");var viewEngine = services.GetRequiredService<IRazorViewEngine>();var view = viewEngine.GetView(null, "~/Pages/IeAlert.cshtml", true)?.View;if (view != null){ ???using (view as IDisposable) ???{ ???????await executor.ExecuteAsync(ControllerContext, view, ViewData, TempData, "text/html; charset=utf-8", 200); ???} ???return new EmptyResult();}ASP.NET Core 2.1 中 ViewResultExecutor 的变化
原文地址：https://www.cnblogs.com/dudu/p/9060857.html