How to Render Views as Strings in .NET Core?

Return View as String in .NET Core

Problem:

Many available articles provide guidance on rendering views to strings in ASP.NET, but not specifically for .NET Core. The .NET Core implementation triggers compilation errors despite attempts at conversion.

Using Statements:

To address this issue, the following using statements are necessary:

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;

Project.json Dependencies:

The corresponding project.json dependencies are:

{
  "dependencies": {
    "Microsoft.AspNetCore.Mvc": "1.1.0",

    ...
  },
}

Controller Extension Method:

The following extension method can be implemented to render views as strings in .NET Core:

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 Example:

The extension method can be invoked from within a controller using the following syntax:

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

For a partial view:

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

This solution provides strong typing for the model, error handling when finding the view, and asynchronous operation.

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