using Microsoft.AspNetCore.Mvc;

using Microsoft.AspNetCore.Mvc.Rendering;

using Microsoft.AspNetCore.Mvc.ViewEngines;

using Microsoft.AspNetCore.Mvc.ViewFeatures;

using System;

using System.Collections.Generic;

using System.IO;

using System.Linq;

using System.Threading.Tasks;

namespace NetCorePortal.Models

{

    public class ViewHtmlHelper

    {

        public static string ConvertToString(Controller controller, string viewName, object viewModel, bool isMainPage)

        {

            controller.ViewData.Model = viewModel;

            using (StringWriter sw = new StringWriter())

            {

                IViewEngine viewEngine = controller.HttpContext.RequestServices.GetService(typeof(ICompositeViewEngine)) as ICompositeViewEngine;

                ViewEngineResult viewEngineResult = viewEngine.FindView(controller.ControllerContext, viewName, isMainPage);

                if (viewEngineResult.Success)

                {

                    ViewContext viewContext = new ViewContext(

                        controller.ControllerContext,

                        viewEngineResult.View,

                        controller.ViewData,

                        controller.TempData,

                       sw,

                       new HtmlHelperOptions()

                        );

                    viewEngineResult.View.RenderAsync(viewContext);

                    return sw.GetStringBuilder().ToString();

                }

                else

                {

                    return $"视图{viewName}不存在";

                }

            }

        }

    }

}

public ContentResult ViewToStringDemo()

{

    string strView = ViewHtmlHelper.ConvertToString(this, "Index", "", true);

    return Content(strView);

}

/// <summary>

/// 获得LayTreeGrid视图的HTML内容

/// </summary>

/// <returns></returns>

public ContentResult ViewText()

{

     string html = string.Empty;

     IView view = ViewEngines.Engines.FindView(this.ControllerContext, "LayTreegrid", null).View;

     ViewDataDictionary vdd = new ViewDataDictionary();

     TempDataDictionary tdd = new TempDataDictionary();

     using (System.IO.StringWriter sw = new System.IO.StringWriter())

     {

         ViewContext viewContext = new ViewContext(this.ControllerContext, view, vdd, tdd, sw);

         viewContext.View.Render(viewContext, sw);

         html = sw.ToString();

     }

     return Content(html);

}