how to call html action in asp net core

1using System;
2using System.IO;
3using System.Linq;
4using System.Threading.Tasks;
5using Microsoft.AspNetCore.Html;
6using Microsoft.AspNetCore.Http;
7using Microsoft.AspNetCore.Http.Extensions;
8using Microsoft.AspNetCore.Mvc;
9using Microsoft.AspNetCore.Mvc.Controllers;
10using Microsoft.AspNetCore.Mvc.Internal;
11using Microsoft.AspNetCore.Mvc.Infrastructure;
12using Microsoft.AspNetCore.Mvc.Razor;
13using Microsoft.AspNetCore.Mvc.Rendering;
14using Microsoft.AspNetCore.Routing;
15
16namespace Microsoft.AspNetCore.Mvc.Rendering    {
17
18    public static class HtmlHelperViewExtensions
19    {
20
21        public static IHtmlContent RenderAction(this IHtmlHelper helper, string action, object parameters = null)
22        {
23            var controller =  (string)helper.ViewContext.RouteData.Values["controller"];
24
25            return RenderAction(helper, action, controller, parameters);
26        }
27
28        public static IHtmlContent RenderAction(this IHtmlHelper helper, string action, string controller, object parameters = null)
29        {
30            var area = (string)helper.ViewContext.RouteData.Values["area"];
31
32            return RenderAction(helper, action, controller, area, parameters);
33        }
34
35        public static IHtmlContent RenderAction(this IHtmlHelper helper, string action, string controller, string area, object parameters = null)
36        {
37            if (action == null)
38                throw new ArgumentNullException("action");
39
40            if (controller == null)
41                throw new ArgumentNullException("controller");
42
43            if (area == null)
44                throw new ArgumentNullException("area");
45
46            var task = RenderActionAsync(helper, action, controller, area, parameters);
47
48            return task.Result;
49        }
50
51        private static async Task<IHtmlContent> RenderActionAsync(this IHtmlHelper helper, string action, string controller, string area, object parameters = null)
52        {
53            // fetching required services for invocation
54            var currentHttpContext = helper.ViewContext?.HttpContext;
55            var httpContextFactory = GetServiceOrFail<IHttpContextFactory>(currentHttpContext);
56            var actionInvokerFactory = GetServiceOrFail<IActionInvokerFactory>(currentHttpContext);
57            var actionSelector = GetServiceOrFail<IActionSelectorDecisionTreeProvider>(currentHttpContext);
58
59            // creating new action invocation context
60            var routeData = new RouteData();
61            var routeParams = new RouteValueDictionary(parameters ?? new { });
62            var routeValues = new RouteValueDictionary(new { area = area, controller = controller, action = action });
63            var newHttpContext = httpContextFactory.Create(currentHttpContext.Features);
64
65            newHttpContext.Response.Body = new MemoryStream();
66
67            foreach (var router in helper.ViewContext.RouteData.Routers)
68                routeData.PushState(router, null, null);
69
70            routeData.PushState(null, routeValues, null);
71            routeData.PushState(null, routeParams, null);
72
73            var actionDescriptor = actionSelector.DecisionTree.Select(routeValues).First();
74            var actionContext = new ActionContext(newHttpContext, routeData, actionDescriptor);
75
76            // invoke action and retreive the response body
77            var invoker = actionInvokerFactory.CreateInvoker(actionContext);
78            string content = null;
79
80            await invoker.InvokeAsync().ContinueWith(task => {
81                if (task.IsFaulted)
82                {
83                    content = task.Exception.Message;
84                }
85                else if (task.IsCompleted)
86                {
87                    newHttpContext.Response.Body.Position = 0;
88                    using (var reader = new StreamReader(newHttpContext.Response.Body))
89                        content = reader.ReadToEnd();
90                }
91            });
92
93            return new HtmlString(content);
94        }
95
96        private static TService GetServiceOrFail<TService>(HttpContext httpContext)
97        {
98            if (httpContext == null)
99                throw new ArgumentNullException(nameof(httpContext));
100
101            var service = httpContext.RequestServices.GetService(typeof(TService));
102
103            if (service == null)
104                throw new InvalidOperationException($"Could not locate service: {nameof(TService)}");
105
106            return (TService)service;
107        }
108    }
109}