Introduced SetViewDataAsync on UmbracoViewPage

Signed-off-by: Bjarke Berg <mail@bergmania.dk>

src/Umbraco.Web.Common/AspNetCore/UmbracoViewPage.cs

@@ -1,7 +1,10 @@
 using System;
 using System.Text;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http.Extensions;
+using Microsoft.AspNetCore.Mvc.ModelBinding;
 using Microsoft.AspNetCore.Mvc.Razor;
+using Microsoft.AspNetCore.Mvc.ViewFeatures;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Options;
 using Umbraco.Core;
@@ -11,6 +14,7 @@ using Umbraco.Core.IO;
 using Umbraco.Core.Logging;
 using Umbraco.Core.Models.PublishedContent;
 using Umbraco.Core.Strings;
+using Umbraco.Web.Common.ModelBinders;
 
 namespace Umbraco.Web.Common.AspNetCore
 {
@@ -29,6 +33,7 @@ namespace Umbraco.Web.Common.AspNetCore
         private ContentSettings ContentSettings => Context.RequestServices.GetRequiredService<IOptions<ContentSettings>>().Value;
         private IProfilerHtml ProfilerHtml => Context.RequestServices.GetRequiredService<IProfilerHtml>();
         private IIOHelper IOHelper => Context.RequestServices.GetRequiredService<IIOHelper>();
+        private ContentModelBinder ContentModelBinder => new ContentModelBinder();
 
         protected IUmbracoContext UmbracoContext => _umbracoContext ??= UmbracoContextAccessor.UmbracoContext;
 
@@ -85,5 +90,58 @@ namespace Umbraco.Web.Common.AspNetCore
 
             base.WriteLiteral(value);
         }
+
+        // maps model
+        protected async Task SetViewDataAsync(ViewDataDictionary viewData)
+        {
+            // capture the model before we tinker with the viewData
+            var viewDataModel = viewData.Model;
+
+            // map the view data (may change its type, may set model to null)
+            viewData = MapViewDataDictionary(viewData, typeof (TModel));
+
+            // bind the model
+            var bindingContext = new DefaultModelBindingContext();
+            await ContentModelBinder.BindModelAsync(bindingContext, viewDataModel, typeof (TModel));
+
+            viewData.Model = bindingContext.Result.Model;
+
+            // set the view data
+            ViewData = (ViewDataDictionary<TModel>) viewData;
+        }
+
+        // viewData is the ViewDataDictionary (maybe <TModel>) that we have
+        // modelType is the type of the model that we need to bind to
+        //
+        // figure out whether viewData can accept modelType else replace it
+        //
+        private static ViewDataDictionary MapViewDataDictionary(ViewDataDictionary viewData, Type modelType)
+        {
+            var viewDataType = viewData.GetType();
+
+
+            if (viewDataType.IsGenericType)
+            {
+                // ensure it is the proper generic type
+                var def = viewDataType.GetGenericTypeDefinition();
+                if (def != typeof(ViewDataDictionary<>))
+                    throw new Exception("Could not map viewData of type \"" + viewDataType.FullName + "\".");
+
+                // get the viewData model type and compare with the actual view model type:
+                // viewData is ViewDataDictionary<viewDataModelType> and we will want to assign an
+                // object of type modelType to the Model property of type viewDataModelType, we
+                // need to check whether that is possible
+                var viewDataModelType = viewDataType.GenericTypeArguments[0];
+
+                if (viewDataModelType.IsAssignableFrom(modelType))
+                    return viewData;
+            }
+
+            // if not possible or it is not generic then we need to create a new ViewDataDictionary
+            var nViewDataType = typeof(ViewDataDictionary<>).MakeGenericType(modelType);
+            var tViewData = new ViewDataDictionary(viewData) { Model = null }; // temp view data to copy values
+            var nViewData = (ViewDataDictionary)Activator.CreateInstance(nViewDataType, tViewData);
+            return nViewData;
+        }
     }
 }