Add RazorViewToStringRenderer

src/RazorHtmlEmails.RazorClassLib/Services/RazorViewToStringRenderer.cs

@@ -0,0 +1,97 @@
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Mvc.Abstractions;
+using Microsoft.AspNetCore.Mvc.ModelBinding;
+using Microsoft.AspNetCore.Mvc.Razor;
+using Microsoft.AspNetCore.Mvc.Rendering;
+using Microsoft.AspNetCore.Mvc.ViewEngines;
+using Microsoft.AspNetCore.Mvc.ViewFeatures;
+using Microsoft.AspNetCore.Routing;
+using System;
+using System.IO;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace RazorHtmlEmails.RazorClassLib.Services
+{
+    // Code from: https://github.com/aspnet/Entropy/blob/dev/samples/Mvc.RenderViewToString/RazorViewToStringRenderer.cs
+
+    public class RazorViewToStringRenderer : IRazorViewToStringRenderer
+    {
+        private IRazorViewEngine _viewEngine;
+        private ITempDataProvider _tempDataProvider;
+        private IServiceProvider _serviceProvider;
+
+        public RazorViewToStringRenderer(
+            IRazorViewEngine viewEngine,
+            ITempDataProvider tempDataProvider,
+            IServiceProvider serviceProvider)
+        {
+            _viewEngine = viewEngine;
+            _tempDataProvider = tempDataProvider;
+            _serviceProvider = serviceProvider;
+        }
+
+        public async Task<string> RenderViewToStringAsync<TModel>(string viewName, TModel model)
+        {
+            var actionContext = GetActionContext();
+            var view = FindView(actionContext, viewName);
+
+            using (var output = new StringWriter())
+            {
+                var viewContext = new ViewContext(
+                    actionContext,
+                    view,
+                    new ViewDataDictionary<TModel>(
+                        metadataProvider: new EmptyModelMetadataProvider(),
+                        modelState: new ModelStateDictionary())
+                    {
+                        Model = model
+                    },
+                    new TempDataDictionary(
+                        actionContext.HttpContext,
+                        _tempDataProvider),
+                    output,
+                    new HtmlHelperOptions());
+
+                await view.RenderAsync(viewContext);
+
+                return output.ToString();
+            }
+        }
+
+        private IView FindView(ActionContext actionContext, string viewName)
+        {
+            var getViewResult = _viewEngine.GetView(executingFilePath: null, viewPath: viewName, isMainPage: true);
+            if (getViewResult.Success)
+            {
+                return getViewResult.View;
+            }
+
+            var findViewResult = _viewEngine.FindView(actionContext, viewName, isMainPage: true);
+            if (findViewResult.Success)
+            {
+                return findViewResult.View;
+            }
+
+            var searchedLocations = getViewResult.SearchedLocations.Concat(findViewResult.SearchedLocations);
+            var errorMessage = string.Join(
+                Environment.NewLine,
+                new[] { $"Unable to find view '{viewName}'. The following locations were searched:" }.Concat(searchedLocations)); ;
+
+            throw new InvalidOperationException(errorMessage);
+        }
+
+        private ActionContext GetActionContext()
+        {
+            var httpContext = new DefaultHttpContext();
+            httpContext.RequestServices = _serviceProvider;
+            return new ActionContext(httpContext, new RouteData(), new ActionDescriptor());
+        }
+
+    }
+    public interface IRazorViewToStringRenderer
+    {
+        Task<string> RenderViewToStringAsync<TModel>(string viewName, TModel model);
+    }
+}