Render a Razor view in ASP.NET Core 2.1. The view name should be in "~/path/to/view.cshtml" form

RazorViewRenderer.cs

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc.ModelBinding;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewEngines;
using Microsoft.AspNetCore.Mvc.ViewFeatures;

public class RazorViewRenderer
{
    private readonly ICompositeViewEngine _viewEngine;
    private readonly IServiceProvider _serviceProvider;

    public RazorViewRenderer(ICompositeViewEngine viewEngine, IServiceProvider serviceProvider)
    {
        _viewEngine = viewEngine;
        _serviceProvider = serviceProvider;
    }

    public async Task<string> RenderView(string viewName, object model, IDictionary<string, object> viewData = null)
    {
        var viewResult = _viewEngine.GetView(null, viewName, false);
        if (!viewResult.Success)
            throw new Exception("View not found.");

        var data = new ViewDataDictionary(new EmptyModelMetadataProvider(), new ModelStateDictionary()) { Model = model };
        if (viewData != null)
        {
            foreach (var (key, value) in viewData)
                data.Add(key, value);
        }

        using (var sw = new System.IO.StringWriter())
        {
            var viewContext = new ViewContext
            {
                HttpContext = new DefaultHttpContext { RequestServices = _serviceProvider },
                View = viewResult.View,
                ViewData = data,
                Writer = sw,
            };

            await viewResult.View.RenderAsync(viewContext);
            return sw.ToString();
        }
    }
}