Fixes: U4-6937 Update all web.configs in all subfolders to use MVC4 / Razor 3, U4-6938 While upgrading, delete dlls that shouldn't be there after upgrade

src/Umbraco.Web.UI/umbraco/Install/Views/Web.config

@@ -1,4 +1,4 @@
-<?xml version="1.0"?>
+<?xml version="1.0"?>
 
 <configuration>
   <configSections>

src/Umbraco.Web/Install/InstallHelper.cs

@@ -46,6 +46,7 @@ namespace Umbraco.Web.Install
                 new UpgradeStep(),
                 new FilePermissionsStep(),
                 new MajorVersion7UpgradeReport(_umbContext.Application),
+                new Version73FileCleanup(_umbContext.HttpContext, _umbContext.Application.ProfilingLogger.Logger),
                 new DatabaseConfigureStep(_umbContext.Application),
                 new DatabaseInstallStep(_umbContext.Application),
                 new DatabaseUpgradeStep(_umbContext.Application),

src/Umbraco.Web/Install/InstallSteps/Version73FileCleanup.cs

@@ -0,0 +1,90 @@
+using System;
+using System.IO;
+using System.Text;
+using System.Text.RegularExpressions;
+using System.Threading;
+using System.Web;
+using Umbraco.Core.Configuration;
+using Umbraco.Core.Logging;
+using Umbraco.Web.Install.Models;
+
+namespace Umbraco.Web.Install.InstallSteps
+{
+    [InstallSetupStep(InstallationType.Upgrade,
+        "Version73FileCleanup", 2, 
+        "Performing some housecleaning...", 
+        PerformsAppRestart = true)]
+    internal class Version73FileCleanup : InstallSetupStep<object>
+    {
+        private readonly HttpContextBase _httpContext;
+        private readonly ILogger _logger;
+
+        public Version73FileCleanup(HttpContextBase httpContext, ILogger logger)
+        {
+            _httpContext = httpContext;
+            _logger = logger;
+        }
+
+        /// <summary>
+        /// The step execution method
+        /// </summary>
+        /// <param name="model"></param>
+        /// <returns></returns>
+        public override InstallSetupResult Execute(object model)
+        {
+            //first cleanup all web.configs
+
+            var root = new DirectoryInfo(_httpContext.Server.MapPath("~/"));
+            ProcessWebConfigs(root);
+            
+            //now remove the dll 
+
+            var bin = root.GetDirectories("bin", SearchOption.TopDirectoryOnly);
+            if (bin.Length == 1)
+            {
+                var dll = bin[0].GetFiles("Microsoft.Web.Mvc.FixedDisplayModes.dll", SearchOption.TopDirectoryOnly);
+                if (dll.Length == 1)
+                {
+                    _logger.Info<Version73FileCleanup>("Deleting non-compatible and no longer used DLL: {0}", () => dll[0].FullName);
+                    File.Delete(dll[0].FullName);
+                }
+            }
+
+            return null;
+        }
+
+        /// <summary>
+        /// Determines if this step needs to execute based on the current state of the application and/or install process
+        /// </summary>
+        /// <returns></returns>
+        public override bool RequiresExecution(object model)
+        {
+            return UmbracoVersion.Current == Version.Parse("7.3.0");
+        }
+
+        private void ProcessWebConfigs(DirectoryInfo dir)
+        {
+            //Do the processing of files
+            var found = dir.GetFiles("web.config", SearchOption.AllDirectories);
+
+            foreach (var configFile in found)
+            {
+                var fileName = configFile.FullName;
+                _logger.Info<Version73FileCleanup>("Cleaning up web.config file: {0}", () => fileName);
+
+                var contents = File.ReadAllText(fileName);
+                contents = _microsoftWebHelpers.Replace(contents, string.Empty);
+                contents = _webPagesRazorVersion.Replace(contents, "$1=3.0.0.0");
+                contents = _mvcVersion.Replace(contents, "$1=5.2.3.0");
+                using (var writer = new StreamWriter(configFile.FullName, false))
+                {
+                    writer.Write(contents);
+                }
+            }
+        }
+
+        private readonly Regex _microsoftWebHelpers = new Regex(@"<add\s*?namespace=""Microsoft\.Web\.Helpers""\s*?/>", RegexOptions.Compiled);
+        private readonly Regex _webPagesRazorVersion = new Regex(@"(System\.Web\.WebPages\.Razor,\s*?Version)(=2\.0\.0\.0)", RegexOptions.Compiled);
+        private readonly Regex _mvcVersion = new Regex(@"(System\.Web\.Mvc,\s*?Version)(=4\.0\.0\.0)", RegexOptions.Compiled);
+    }
+}

src/Umbraco.Web/Umbraco.Web.csproj

@@ -300,6 +300,7 @@
     <Compile Include="BatchedDatabaseServerMessengerStartup.cs" />
     <Compile Include="Editors\BackOfficeNotificationsController.cs" />
     <Compile Include="HtmlHelperBackOfficeExtensions.cs" />
+    <Compile Include="Install\InstallSteps\Version73FileCleanup.cs" />
     <Compile Include="Media\EmbedProviders\Flickr.cs" />
     <Compile Include="Models\ContentEditing\SimpleNotificationModel.cs" />
     <Compile Include="PropertyEditors\DatePreValueEditor.cs" />