render actionin a view asp.net core code example

Example 1: how to call html.action in asp.net core

using System;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Html;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Http.Extensions;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Controllers;
using Microsoft.AspNetCore.Mvc.Internal;
using Microsoft.AspNetCore.Mvc.Infrastructure;
using Microsoft.AspNetCore.Mvc.Razor;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Routing;

namespace Microsoft.AspNetCore.Mvc.Rendering    {

    public static class HtmlHelperViewExtensions
    {

        public static IHtmlContent RenderAction(this IHtmlHelper helper, string action, object parameters = null)
        {
            var controller =  (string)helper.ViewContext.RouteData.Values["controller"];

            return RenderAction(helper, action, controller, parameters);
        }

        public static IHtmlContent RenderAction(this IHtmlHelper helper, string action, string controller, object parameters = null)
        {
            var area = (string)helper.ViewContext.RouteData.Values["area"];

            return RenderAction(helper, action, controller, area, parameters);
        }

        public static IHtmlContent RenderAction(this IHtmlHelper helper, string action, string controller, string area, object parameters = null)
        {
            if (action == null)
                throw new ArgumentNullException("action");

            if (controller == null)
                throw new ArgumentNullException("controller");

            if (area == null)
                throw new ArgumentNullException("area");

            var task = RenderActionAsync(helper, action, controller, area, parameters);

            return task.Result;
        }

        private static async Task<IHtmlContent> RenderActionAsync(this IHtmlHelper helper, string action, string controller, string area, object parameters = null)
        {
            // fetching required services for invocation
            var currentHttpContext = helper.ViewContext?.HttpContext;
            var httpContextFactory = GetServiceOrFail<IHttpContextFactory>(currentHttpContext);
            var actionInvokerFactory = GetServiceOrFail<IActionInvokerFactory>(currentHttpContext);
            var actionSelector = GetServiceOrFail<IActionSelectorDecisionTreeProvider>(currentHttpContext);

            // creating new action invocation context
            var routeData = new RouteData();
            var routeParams = new RouteValueDictionary(parameters ?? new { });
            var routeValues = new RouteValueDictionary(new { area = area, controller = controller, action = action });
            var newHttpContext = httpContextFactory.Create(currentHttpContext.Features);

            newHttpContext.Response.Body = new MemoryStream();

            foreach (var router in helper.ViewContext.RouteData.Routers)
                routeData.PushState(router, null, null);

            routeData.PushState(null, routeValues, null);
            routeData.PushState(null, routeParams, null);

            var actionDescriptor = actionSelector.DecisionTree.Select(routeValues).First();
            var actionContext = new ActionContext(newHttpContext, routeData, actionDescriptor);

            // invoke action and retreive the response body
            var invoker = actionInvokerFactory.CreateInvoker(actionContext);
            string content = null;

            await invoker.InvokeAsync().ContinueWith(task => {
                if (task.IsFaulted)
                {
                    content = task.Exception.Message;
                }
                else if (task.IsCompleted)
                {
                    newHttpContext.Response.Body.Position = 0;
                    using (var reader = new StreamReader(newHttpContext.Response.Body))
                        content = reader.ReadToEnd();
                }
            });

            return new HtmlString(content);
        }

        private static TService GetServiceOrFail<TService>(HttpContext httpContext)
        {
            if (httpContext == null)
                throw new ArgumentNullException(nameof(httpContext));

            var service = httpContext.RequestServices.GetService(typeof(TService));

            if (service == null)
                throw new InvalidOperationException($"Could not locate service: {nameof(TService)}");

            return (TService)service;
        }
    }
}

Example 2: mvc core 3.1 render action to string

using System;using System.IO;using System.Linq;using System.Threading.Tasks;using Microsoft.AspNetCore.Http;using Microsoft.AspNetCore.Mvc;using Microsoft.AspNetCore.Mvc.Abstractions;using Microsoft.AspNetCore.Mvc.ModelBinding;using Microsoft.AspNetCore.Mvc.Razor;using Microsoft.AspNetCore.Mvc.Rendering;using Microsoft.AspNetCore.Mvc.ViewEngines;using Microsoft.AspNetCore.Mvc.ViewFeatures;using Microsoft.AspNetCore.Routing;namespace RazorPartialToString.Services{    public class RazorPartialToStringRenderer : IRazorPartialToStringRenderer    {        private IRazorViewEngine _viewEngine;        private ITempDataProvider _tempDataProvider;        private IServiceProvider _serviceProvider;        public RazorPartialToStringRenderer(            IRazorViewEngine viewEngine,            ITempDataProvider tempDataProvider,            IServiceProvider serviceProvider)        {            _viewEngine = viewEngine;            _tempDataProvider = tempDataProvider;            _serviceProvider = serviceProvider;        }        public async Task<string> RenderPartialToStringAsync<TModel>(string partialName, TModel model)        {            var actionContext = GetActionContext();            var partial = FindView(actionContext, partialName);            using (var output = new StringWriter())            {                var viewContext = new ViewContext(                    actionContext,                    partial,                    new ViewDataDictionary<TModel>(                        metadataProvider: new EmptyModelMetadataProvider(),                        modelState: new ModelStateDictionary())                    {                        Model = model                    },                    new TempDataDictionary(                        actionContext.HttpContext,                        _tempDataProvider),                    output,                    new HtmlHelperOptions()                );                await partial.RenderAsync(viewContext);                return output.ToString();            }        }        private IView FindView(ActionContext actionContext, string partialName)        {            var getPartialResult = _viewEngine.GetView(null, partialName, false);            if (getPartialResult.Success)            {                return getPartialResult.View;            }            var findPartialResult = _viewEngine.FindView(actionContext, partialName, false);            if (findPartialResult.Success)            {                return findPartialResult.View;            }            var searchedLocations = getPartialResult.SearchedLocations.Concat(findPartialResult.SearchedLocations);            var errorMessage = string.Join(                Environment.NewLine,                new[] { $"Unable to find partial '{partialName}'. The following locations were searched:" }.Concat(searchedLocations)); ;            throw new InvalidOperationException(errorMessage);        }        private ActionContext GetActionContext()        {            var httpContext = new DefaultHttpContext            {                RequestServices = _serviceProvider            };            return new ActionContext(httpContext, new RouteData(), new ActionDescriptor());        }    }}