diff --git a/src/Umbraco.Core/Persistence/Repositories/DataTypeDefinitionRepository.cs b/src/Umbraco.Core/Persistence/Repositories/DataTypeDefinitionRepository.cs
index 7cd7069751..d8bfe62deb 100644
--- a/src/Umbraco.Core/Persistence/Repositories/DataTypeDefinitionRepository.cs
+++ b/src/Umbraco.Core/Persistence/Repositories/DataTypeDefinitionRepository.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Data;
 using System.Globalization;
 using System.Linq;
 using Umbraco.Core.Models;
@@ -8,6 +9,7 @@ using Umbraco.Core.Models.Rdbms;
 using Umbraco.Core.Persistence.Caching;
 using Umbraco.Core.Persistence.Factories;
 using Umbraco.Core.Persistence.Querying;
+using Umbraco.Core.Persistence.SqlSyntax;
 using Umbraco.Core.Persistence.UnitOfWork;
 
 namespace Umbraco.Core.Persistence.Repositories
@@ -119,6 +121,15 @@ namespace Umbraco.Core.Persistence.Repositories
         {
             ((DataTypeDefinition)entity).AddingEntity();
 
+            //Cannot add a duplicate data type
+            var exists = Database.ExecuteScalar<int>(@"SELECT COUNT(*) FROM cmsDataType
+INNER JOIN umbracoNode ON cmsDataType.nodeId = umbracoNode.id
+WHERE umbracoNode." + SqlSyntaxContext.SqlSyntaxProvider.GetQuotedColumnName("text") + "= @name", new {name = entity.Name});
+            if (exists > 0)
+            {
+                throw new DuplicateNameException("A data type with the name " + entity.Name + " already exists");
+            }
+
             var factory = new DataTypeDefinitionFactory(NodeObjectTypeId);
             var dto = factory.BuildDto(entity);
 
diff --git a/src/Umbraco.Tests/Persistence/Repositories/DataTypeDefinitionRepositoryTest.cs b/src/Umbraco.Tests/Persistence/Repositories/DataTypeDefinitionRepositoryTest.cs
index fc4ad0fd05..4becdc9556 100644
--- a/src/Umbraco.Tests/Persistence/Repositories/DataTypeDefinitionRepositoryTest.cs
+++ b/src/Umbraco.Tests/Persistence/Repositories/DataTypeDefinitionRepositoryTest.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Data;
 using System.Linq;
 using NUnit.Framework;
 using Umbraco.Core;
@@ -28,6 +29,57 @@ namespace Umbraco.Tests.Persistence.Repositories
             return dataTypeDefinitionRepository;
         }
 
+        [Test]
+        public void Can_Create()
+        {
+            var provider = new PetaPocoUnitOfWorkProvider();
+            var unitOfWork = provider.GetUnitOfWork();
+            int id;
+            using (var repository = CreateRepository(unitOfWork))
+            {
+                var dataTypeDefinition = new DataTypeDefinition(-1, new Guid(Constants.PropertyEditors.RadioButtonList)) {Name = "test"};
+
+                repository.AddOrUpdate(dataTypeDefinition);
+
+                unitOfWork.Commit();
+                id = dataTypeDefinition.Id;
+                Assert.That(id, Is.GreaterThan(0));
+            }
+            using (var repository = CreateRepository(unitOfWork))
+            {
+                // Act
+                var dataTypeDefinition = repository.Get(id);
+
+                // Assert
+                Assert.That(dataTypeDefinition, Is.Not.Null);
+                Assert.That(dataTypeDefinition.HasIdentity, Is.True);
+            }
+        }
+
+        [Test]
+        public void Cannot_Create_Duplicate_Name()
+        {
+            var provider = new PetaPocoUnitOfWorkProvider();
+            var unitOfWork = provider.GetUnitOfWork();
+            int id;
+            using (var repository = CreateRepository(unitOfWork))
+            {
+                var dataTypeDefinition = new DataTypeDefinition(-1, new Guid(Constants.PropertyEditors.RadioButtonList)) { Name = "test" };
+                repository.AddOrUpdate(dataTypeDefinition);
+                unitOfWork.Commit();
+                id = dataTypeDefinition.Id;
+                Assert.That(id, Is.GreaterThan(0));
+            }
+            using (var repository = CreateRepository(unitOfWork))
+            {
+                var dataTypeDefinition = new DataTypeDefinition(-1, new Guid(Constants.PropertyEditors.RadioButtonList)) { Name = "test" };
+                repository.AddOrUpdate(dataTypeDefinition);
+
+                Assert.Throws<DuplicateNameException>(unitOfWork.Commit);
+                
+            }
+        }
+
         [Test]
         public void Can_Instantiate_Repository_From_Resolver()
         {
diff --git a/src/Umbraco.Web.UI/umbraco/create/simple.ascx b/src/Umbraco.Web.UI/umbraco/create/simple.ascx
index 89ef19ede0..4a965a4eb1 100644
--- a/src/Umbraco.Web.UI/umbraco/create/simple.ascx
+++ b/src/Umbraco.Web.UI/umbraco/create/simple.ascx
@@ -1,4 +1,4 @@
-<%@ Control Language="c#" AutoEventWireup="True" Codebehind="simple.ascx.cs" Inherits="umbraco.cms.presentation.create.controls.simple" TargetSchema="http://schemas.microsoft.com/intellisense/ie5" %>
+<%@ Control Language="c#" AutoEventWireup="True" Inherits="umbraco.cms.presentation.create.controls.simple" TargetSchema="http://schemas.microsoft.com/intellisense/ie5" %>
 <%@ Register TagPrefix="cc1" Namespace="umbraco.uicontrols" Assembly="controls" %>
 
 
@@ -13,9 +13,10 @@
      <asp:Button id="sbmt" Runat="server" CssClass="btn btn-primary" onclick="sbmt_Click"></asp:Button>
 </cc1:Pane>
 
+    
 
 <!-- added to support missing postback on enter in IE -->
 <asp:TextBox runat="server" style="visibility:hidden;display:none;" ID="Textbox1"/>
+<asp:CustomValidator runat="server" ID="CustomValidation" style="color:#8a1f11;display:block;"></asp:CustomValidator>
 <input type="hidden" name="nodeType">
 
-
diff --git a/src/Umbraco.Web/Umbraco.Web.csproj b/src/Umbraco.Web/Umbraco.Web.csproj
index 5969bee701..49169694a6 100644
--- a/src/Umbraco.Web/Umbraco.Web.csproj
+++ b/src/Umbraco.Web/Umbraco.Web.csproj
@@ -683,6 +683,9 @@
     <Compile Include="umbraco.presentation\umbraco\controls\Tree\TreeControl.ascx.cs">
       <SubType>ASPXCodeBehind</SubType>
     </Compile>
+    <Compile Include="umbraco.presentation\umbraco\create\simple.ascx.cs">
+      <SubType>ASPXCodeBehind</SubType>
+    </Compile>
     <Compile Include="umbraco.presentation\umbraco\developer\Packages\directoryBrowser.aspx.cs">
       <SubType>ASPXCodeBehind</SubType>
     </Compile>
@@ -1274,13 +1277,6 @@
     <Compile Include="umbraco.presentation\umbraco\create\script.ascx.designer.cs">
       <DependentUpon>script.ascx</DependentUpon>
     </Compile>
-    <Compile Include="umbraco.presentation\umbraco\create\simple.ascx.cs">
-      <DependentUpon>simple.ascx</DependentUpon>
-      <SubType>ASPXCodeBehind</SubType>
-    </Compile>
-    <Compile Include="umbraco.presentation\umbraco\create\simple.ascx.designer.cs">
-      <DependentUpon>simple.ascx</DependentUpon>
-    </Compile>
     <Compile Include="umbraco.presentation\umbraco\create\languageTasks.cs">
       <SubType>Code</SubType>
     </Compile>
@@ -1958,9 +1954,7 @@
       <SubType>ASPXCodeBehind</SubType>
     </Content>
     <Content Include="umbraco.presentation\umbraco\create\nodeType.ascx" />
-    <Content Include="umbraco.presentation\umbraco\create\simple.ascx">
-      <SubType>ASPXCodeBehind</SubType>
-    </Content>
+
     <Content Include="umbraco.presentation\umbraco\dashboard\LatestEdits.ascx">
       <SubType>ASPXCodeBehind</SubType>
     </Content>
diff --git a/src/Umbraco.Web/umbraco.presentation/umbraco/create/simple.ascx b/src/Umbraco.Web/umbraco.presentation/umbraco/create/simple.ascx
deleted file mode 100644
index d09d4189b3..0000000000
--- a/src/Umbraco.Web/umbraco.presentation/umbraco/create/simple.ascx
+++ /dev/null
@@ -1,18 +0,0 @@
-<%@ Control Language="c#" AutoEventWireup="True" Codebehind="simple.ascx.cs" Inherits="umbraco.cms.presentation.create.controls.simple" TargetSchema="http://schemas.microsoft.com/intellisense/ie5" %>
-<%@ Register TagPrefix="cc1" Namespace="umbraco.uicontrols" Assembly="controls" %>
-
-
-<cc1:Pane runat="server">
-        <cc1:PropertyPanel runat="server" Text="Name">
-             <asp:TextBox id="rename" CssClass="bigInput input-block-level" Runat="server"></asp:TextBox><asp:RequiredFieldValidator id="RequiredFieldValidator1" ErrorMessage="*" ControlToValidate="rename" runat="server">*</asp:RequiredFieldValidator>   
-        </cc1:PropertyPanel> 
-</cc1:Pane>
-
-<div class="btn-toolbar umb-btn-toolbar">
-    <a href="#" class="btn btn-link" onclick="UmbClientMgr.closeModalWindow()"><%=umbraco.ui.Text("cancel")%></a>
-    <asp:Button id="sbmt" Runat="server" CssClass="btn btn-primary" onclick="sbmt_Click"></asp:Button>
-</div>
-
-<!-- added to support missing postback on enter in IE -->
-<asp:TextBox runat="server" style="visibility:hidden;display:none;" ID="Textbox1"/>
-<input type="hidden" name="nodeType">
\ No newline at end of file
diff --git a/src/Umbraco.Web/umbraco.presentation/umbraco/create/simple.ascx.cs b/src/Umbraco.Web/umbraco.presentation/umbraco/create/simple.ascx.cs
index 175990925a..f8d8bb8e1a 100644
--- a/src/Umbraco.Web/umbraco.presentation/umbraco/create/simple.ascx.cs
+++ b/src/Umbraco.Web/umbraco.presentation/umbraco/create/simple.ascx.cs
@@ -1,72 +1,100 @@
-using System.Web;
+using System.Web;
 using System.Web.UI;
 using Umbraco.Core.Logging;
 using Umbraco.Web.UI;
 using Umbraco.Web;
 using System;
 using Umbraco.Web.UI.Controls;
+using System.Web.UI.WebControls;
 using umbraco.BasePages;
 using umbraco.BusinessLogic;
+using Umbraco.Web;
 using UmbracoUserControl = Umbraco.Web.UI.Controls.UmbracoUserControl;
 
 namespace umbraco.cms.presentation.create.controls
 {
     /// <summary>
-	///		Summary description for simple.
-	/// </summary>
+    ///		Summary description for simple.
+    /// </summary>
 	public partial class simple : UmbracoUserControl
-	{
+    {
 
-		protected void Page_Load(object sender, System.EventArgs e)
-		{
-			sbmt.Text = ui.Text("create");
+        protected void Page_Load(object sender, EventArgs e)
+        {
+            sbmt.Text = ui.Text("create");
             rename.Attributes["placeholder"] = ui.Text("name");
 
-			// Put user code to initialize the page here
-		}
+            // Put user code to initialize the page here
+        }
 
-		#region Web Form Designer generated code
-		override protected void OnInit(EventArgs e)
-		{
-			//
-			// CODEGEN: This call is required by the ASP.NET Web Form Designer.
-			//
-			InitializeComponent();
-			base.OnInit(e);
-		}
-		
-		/// <summary>
-		///		Required method for Designer support - do not modify
-		///		the contents of this method with the code editor.
-		/// </summary>
-		private void InitializeComponent()
-		{
-
-		}
-		#endregion
-
-		protected void sbmt_Click(object sender, System.EventArgs e)
-		{
-			if (Page.IsValid) 
-			{
-				int nodeId;
-			    if (int.TryParse(Request.QueryString["nodeId"], out nodeId) == false)
-			        nodeId = -1;
+        protected void sbmt_Click(object sender, EventArgs e)
+        {
+            if (Page.IsValid)
+            {
+                int nodeId;
+                if (int.TryParse(Request.QueryString["nodeId"], out nodeId) == false)
+                    nodeId = -1;
 
+		try
+                {
 
                 var returnUrl = LegacyDialogHandler.Create(
                     new HttpContextWrapper(Context),
                     new User(Security.CurrentUser),
                     Request.GetItemAsString("nodeType"),
-					nodeId,
-					rename.Text.Trim());
+                        nodeId,
+                        rename.Text.Trim());
 
-				BasePage.Current.ClientTools
-					.ChangeContentFrameUrl(returnUrl)
+                    BasePage.Current.ClientTools
+                    .ChangeContentFrameUrl(returnUrl)
 					.ReloadActionNode(false, true)
-					.CloseModalWindow();
+                    .CloseModalWindow();
+                }
+                catch (Exception ex)
+                {
+                    CustomValidation.ErrorMessage = ex.Message;
+                    CustomValidation.IsValid = false;
+                }
             }
-		
-		}
-	}
+
+        }
+
+        protected CustomValidator CustomValidation;
+
+        /// <summary>
+        /// RequiredFieldValidator1 control.
+        /// </summary>
+        /// <remarks>
+        /// Auto-generated field.
+        /// To modify move field declaration from designer file to code-behind file.
+        /// </remarks>
+        protected global::System.Web.UI.WebControls.RequiredFieldValidator RequiredFieldValidator1;
+
+        /// <summary>
+        /// rename control.
+        /// </summary>
+        /// <remarks>
+        /// Auto-generated field.
+        /// To modify move field declaration from designer file to code-behind file.
+        /// </remarks>
+        protected global::System.Web.UI.WebControls.TextBox rename;
+
+        /// <summary>
+        /// Textbox1 control.
+        /// </summary>
+        /// <remarks>
+        /// Auto-generated field.
+        /// To modify move field declaration from designer file to code-behind file.
+        /// </remarks>
+        protected global::System.Web.UI.WebControls.TextBox Textbox1;
+
+        /// <summary>
+        /// sbmt control.
+        /// </summary>
+        /// <remarks>
+        /// Auto-generated field.
+        /// To modify move field declaration from designer file to code-behind file.
+        /// </remarks>
+        protected global::System.Web.UI.WebControls.Button sbmt;
+    }
 }
diff --git a/src/Umbraco.Web/umbraco.presentation/umbraco/create/simple.ascx.designer.cs b/src/Umbraco.Web/umbraco.presentation/umbraco/create/simple.ascx.designer.cs
deleted file mode 100644
index f4bb903739..0000000000
--- a/src/Umbraco.Web/umbraco.presentation/umbraco/create/simple.ascx.designer.cs
+++ /dev/null
@@ -1,51 +0,0 @@
-//------------------------------------------------------------------------------
-// <auto-generated>
-//     This code was generated by a tool.
-//
-//     Changes to this file may cause incorrect behavior and will be lost if
-//     the code is regenerated. 
-// </auto-generated>
-//------------------------------------------------------------------------------
-
-namespace umbraco.cms.presentation.create.controls {
-    
-    
-    public partial class simple {
-        
-        /// <summary>
-        /// rename control.
-        /// </summary>
-        /// <remarks>
-        /// Auto-generated field.
-        /// To modify move field declaration from designer file to code-behind file.
-        /// </remarks>
-        protected global::System.Web.UI.WebControls.TextBox rename;
-        
-        /// <summary>
-        /// RequiredFieldValidator1 control.
-        /// </summary>
-        /// <remarks>
-        /// Auto-generated field.
-        /// To modify move field declaration from designer file to code-behind file.
-        /// </remarks>
-        protected global::System.Web.UI.WebControls.RequiredFieldValidator RequiredFieldValidator1;
-        
-        /// <summary>
-        /// sbmt control.
-        /// </summary>
-        /// <remarks>
-        /// Auto-generated field.
-        /// To modify move field declaration from designer file to code-behind file.
-        /// </remarks>
-        protected global::System.Web.UI.WebControls.Button sbmt;
-        
-        /// <summary>
-        /// Textbox1 control.
-        /// </summary>
-        /// <remarks>
-        /// Auto-generated field.
-        /// To modify move field declaration from designer file to code-behind file.
-        /// </remarks>
-        protected global::System.Web.UI.WebControls.TextBox Textbox1;
-    }
-}
diff --git a/src/Umbraco.Web/umbraco.presentation/umbraco/developer/Macros/assemblyBrowser.aspx.cs b/src/Umbraco.Web/umbraco.presentation/umbraco/developer/Macros/assemblyBrowser.aspx.cs
index 435a75fa09..d186d9ef50 100644
--- a/src/Umbraco.Web/umbraco.presentation/umbraco/developer/Macros/assemblyBrowser.aspx.cs
+++ b/src/Umbraco.Web/umbraco.presentation/umbraco/developer/Macros/assemblyBrowser.aspx.cs
@@ -44,11 +44,7 @@ namespace umbraco.developer
                 if (Request.QueryString["type"] == null)
                 {
                     isUserControl = true;
-                    var fileName = Request.QueryString["fileName"];
-                    //yes this is crap but the ClearnForXss cleans / - so this is a shortcut
-
-                    fileName = fileName.Replace('/', '@').CleanForXss().Replace('@', '/');
-
+                    var fileName = Request.GetItemAsString("fileName");
                     if (!fileName.StartsWith("~"))
                     {
                         if (fileName.StartsWith("/"))
@@ -116,7 +112,7 @@ namespace umbraco.developer
             }
             catch (Exception err)
             {
-                AssemblyName.Text = "Error reading " + Request["fileName"];
+                AssemblyName.Text = "Error reading " + Request.CleanForXss("fileName");
                 Button1.Visible = false;
                 ChooseProperties.Controls.Add(new LiteralControl("<p class=\"guiDialogNormal\" style=\"color: red;\">" + err.ToString() + "</p><p/><p class=\"guiDialogNormal\">"));
             }
diff --git a/src/umbraco.cms/businesslogic/datatype/DataTypeDefinition.cs b/src/umbraco.cms/businesslogic/datatype/DataTypeDefinition.cs
index bcb8c91fa3..c58f9ac17e 100644
--- a/src/umbraco.cms/businesslogic/datatype/DataTypeDefinition.cs
+++ b/src/umbraco.cms/businesslogic/datatype/DataTypeDefinition.cs
@@ -1,9 +1,11 @@
 using System;
 using System.Collections;
 using System.Globalization;
+using System.Data;
 using System.Linq;
 using Umbraco.Core.Cache;
 using Umbraco.Core.Persistence;
+using Umbraco.Core.Persistence.SqlSyntax;
 using Umbraco.Core.PropertyEditors;
 using umbraco.DataLayer;
 using System.Xml;
@@ -265,6 +267,14 @@ namespace umbraco.cms.businesslogic.datatype
         /// <returns></returns>
         public static DataTypeDefinition MakeNew(BusinessLogic.User u, string Text, Guid UniqueId)
         {
+            //Cannot add a duplicate data type
+            var exists = Database.ExecuteScalar<int>(@"SELECT COUNT(*) FROM cmsDataType
+INNER JOIN umbracoNode ON cmsDataType.nodeId = umbracoNode.id
+WHERE umbracoNode." + SqlSyntaxContext.SqlSyntaxProvider.GetQuotedColumnName("text") + "= @name", new { name = Text });
+            if (exists > 0)
+            {
+                throw new DuplicateNameException("A data type with the name " + Text + " already exists");
+            }
 
             var newId = MakeNew(-1, ObjectType, u.Id, 1, Text, UniqueId).Id;