How to Render Views as Strings in .NET Core Controllers?

Rendering Views as Strings in .NET Core with Controller Extension

This article aims to assist you in converting the existing code for rendering views to strings in ASP.NET to work seamlessly with .NET Core.

The provided code assumes a Controller method calling the RenderViewToString method. However, when adapting it to .NET Core, you may encounter compilation errors. This article presents a modified version of the code specifically designed for .NET Core.

Modified Code:

The following code snippet provides an enhanced version of the RenderViewToString method as a Controller extension:

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewEngines;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using System.IO;
using System.Threading.Tasks;

namespace CC.Web.Helpers
{
    public static class ControllerExtensions
    {
        public static async Task<string> RenderViewAsync<TModel>(this Controller controller, string viewName, TModel model, bool partial = false)
        {
            if (string.IsNullOrEmpty(viewName))
            {
                viewName = controller.ControllerContext.ActionDescriptor.ActionName;
            }

            controller.ViewData.Model = model;

            using (var writer = new StringWriter())
            {
                IViewEngine viewEngine = controller.HttpContext.RequestServices.GetService(typeof(ICompositeViewEngine)) as ICompositeViewEngine;
                ViewEngineResult viewResult = viewEngine.FindView(controller.ControllerContext, viewName, !partial);

                if (viewResult.Success == false)
                {
                    return $"A view with the name {viewName} could not be found";
                }

                ViewContext viewContext = new ViewContext(
                    controller.ControllerContext,
                    viewResult.View,
                    controller.ViewData,
                    controller.TempData,
                    writer,
                    new HtmlHelperOptions()
                );

                await viewResult.View.RenderAsync(viewContext);

                return writer.GetStringBuilder().ToString();
            }
        }
    }
}

Usage:

You can use the updated code with the following syntax:

viewHtml = await this.RenderViewAsync("Report", model);

For rendering a PartialView:

partialViewHtml = await this.RenderViewAsync("Report", model, true);

Note:

• This code eliminates the need for dependency injection.
• It provides strong-typing for the model.
• It allows for rendering views as partials or pages.
• It supports asynchronous operations.

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