Updated some of the property editor API to ensure that when formatting data for persistence we have access to the pre-values as well since these might need to be used to format the persisted data. Completed the new property editor: Multiple text box and it is saving the data in a backwards compatible format. Changed the internal AsDictionary method of the pre value collection to be a public method called FormatAsDictionary.

src/Umbraco.Web/Models/ContentEditing/ContentItemDto.cs

@@ -1,4 +1,5 @@
-using Umbraco.Core.Models;
+using Newtonsoft.Json;
+using Umbraco.Core.Models;
 
 namespace Umbraco.Web.Models.ContentEditing
 {

src/Umbraco.Web/Models/ContentEditing/ContentPropertyDto.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using Newtonsoft.Json;
 using Umbraco.Core.Models;
 using Umbraco.Core.PropertyEditors;
 
@@ -14,5 +15,11 @@ namespace Umbraco.Web.Models.ContentEditing
         public string Description { get; set; }
         public bool IsRequired { get; set; }
         public string ValidationRegExp { get; set; }
+
+        /// <summary>
+        /// The current pre-values for this property
+        /// </summary>
+        [JsonIgnore]
+        internal PreValueCollection PreValues { get; set; }
     }
 }