From ffada74aa44bca7aab41da7d690126e03a1660f9 Mon Sep 17 00:00:00 2001
From: Stephan <stephane@umbraco.dk>
Date: Thu, 18 Feb 2016 16:04:45 +0100
Subject: [PATCH] Improve RenderModelBinder error msg when same type, different
 assemblies

---
 src/Umbraco.Web/Mvc/RenderModelBinder.cs | 39 +++++++++++++++++++-----
 1 file changed, 32 insertions(+), 7 deletions(-)

diff --git a/src/Umbraco.Web/Mvc/RenderModelBinder.cs b/src/Umbraco.Web/Mvc/RenderModelBinder.cs
index f8e7ee8a4e..32802ccadc 100644
--- a/src/Umbraco.Web/Mvc/RenderModelBinder.cs
+++ b/src/Umbraco.Web/Mvc/RenderModelBinder.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Globalization;
+using System.Text;
 using System.Web.Mvc;
 using Umbraco.Core;
 using Umbraco.Core.Models;
@@ -31,7 +32,7 @@ namespace Umbraco.Web.Mvc
 		    if (umbracoContext != null && umbracoContext.PublishedContentRequest != null)
 		    {
 		        culture = umbracoContext.PublishedContentRequest.Culture;
-		    }          
+		    }
 
             return BindModel(model, bindingContext.ModelType, culture);
         }
@@ -82,8 +83,7 @@ namespace Umbraco.Web.Mvc
                 if (modelType.Implements<IPublishedContent>())
                 {
                     if ((sourceContent.GetType().Inherits(modelType)) == false)
-                        throw new ModelBindingException(string.Format("Cannot bind source content type {0} to model type {1}.",
-                            sourceContent.GetType(), modelType));
+                        ThrowModelBindingException(true, false, sourceContent.GetType(), modelType);
                     return sourceContent;
                 }
 
@@ -98,8 +98,7 @@ namespace Umbraco.Web.Mvc
                 {
                     var targetContentType = modelType.GetGenericArguments()[0];
                     if ((sourceContent.GetType().Inherits(targetContentType)) == false)
-                        throw new ModelBindingException(string.Format("Cannot bind source content type {0} to model content type {1}.",
-                            sourceContent.GetType(), targetContentType));
+                        ThrowModelBindingException(true, true, sourceContent.GetType(), targetContentType);
                     return Activator.CreateInstance(modelType, sourceContent, culture);
                 }
             }
@@ -109,10 +108,36 @@ namespace Umbraco.Web.Mvc
             if (attempt2.Success) return attempt2.Result;
 
             // fail
-            throw new ModelBindingException(string.Format("Cannot bind source type {0} to model type {1}.",
-                sourceType, modelType));
+            ThrowModelBindingException(false, false, sourceType, modelType);
+            return null;
         }
 
+	    private static void ThrowModelBindingException(bool sourceContent, bool modelContent, Type sourceType, Type modelType)
+	    {
+	        var msg = new StringBuilder();
+
+	        msg.Append("Cannot bind source");
+	        if (sourceContent) msg.Append(" content");
+	        msg.Append(" type ");
+	        msg.Append(sourceType.FullName);
+	        msg.Append(" to model");
+	        if (modelContent) msg.Append(" content");
+	        msg.Append(" type");
+
+	        if (sourceType.FullName == modelType.FullName)
+	        {
+	            msg.Append(". Same type name but different assemblies.");
+	        }
+	        else
+	        {
+	            msg.Append(" ");
+                msg.Append(modelType.FullName);
+                msg.Append(".");
+            }
+
+	        throw new ModelBindingException(msg.ToString());
+	    }
+
         public IModelBinder GetBinder(Type modelType)
         {
             // can bind to RenderModel