So have solved the issue and as usual, a breakdown in logic within my code.

I was creating a new document based on existing properties, then adding the new properties, and then trying to add the values to the new properties. As I had instantiated the new documents prior to adding the new properties, it was failing.

Refactoring the code so that the new properties were added, then the new document created sorted the problem.

Hi Jon

My package isn't in a shape to be able to provide the source code for - sorry, but bad organisational skills :-)

However, below is my helper class that adds the properties to the document type which should be all you need... Only a couple of things to change (NAMESPACE & DOCUMENTTYPE)

using System.Collections.Specialized;
using System.Linq;
using Umbraco.Core.Models;
using Umbraco.Core.Services;

namespace YOURNAMESPACE
{
    public class UmbracoHelper
    {
        private static IDataTypeService dataTypeService = Umbraco.Core.ApplicationContext.Current.Services.DataTypeService;
        private static IDataTypeDefinition[] dataTypeDefinitions = dataTypeService.GetAllDataTypeDefinitions().ToArray();
        private static IDataTypeDefinition definition = dataTypeDefinitions.FirstOrDefault(p => p.Name.ToLower() == "textstring");
        private static IContentTypeService contentTypeService = Umbraco.Core.ApplicationContext.Current.Services.ContentTypeService;
        private static IContentType paypalContentType = contentTypeService.GetContentType(YOURDOCUMENTTYPEHERE));

        public static bool AddDocumentTypeProperty(NameValueCollection docTypeProperties)
        {
            try
            {
                var items = docTypeProperties.AllKeys.SelectMany(docTypeProperties.GetValues, (k, v) => new { key = k, value = v });

                foreach (var item in items)
                {
                    if (!paypalContentType.PropertyTypeExists(item.key.ToLower()))
                    {
                        paypalContentType.AddPropertyType(new PropertyType(definition) { Name = item.key.ToString(), Alias = item.key.ToLower() });
                    }
                }
                contentTypeService.Save(paypalContentType);
                return true;
            }
            catch
            {
                return false;
            }
        }
    }
}

Hope this helps - keep me posted if I can assist further.

Cheers, Nigel

NIgel,

Thanks for this, I am almost there with it too!

Sadly, while your snippet seems to work with a single document type, I'm trying to add this new property to all the instances of certain doctypes, here's my code, which errors on the doctype.AddPropertyType() method with a "Object reference not set to an instance of an object." message:

  private static bool AddLatestNewsToSiteDocTypes()
  {
    try
    {
      //Grab hold of the content type service
      var contentTypeService = UmbracoContext.Current.Application.Services.ContentTypeService;

      //Use the CSO to get all the required doctypes
      var siteContentDocTypes = contentTypeService.GetAllContentTypes().Where(
      node =>
        node.Alias.InvariantEquals("NG_USK_Homepage") ||
        node.Alias.InvariantEquals("NG_USK_FrontPage") ||
        node.Alias.InvariantEquals("NG_USK_StandardPage") ||
        node.Alias.InvariantEquals("NG_USK_StandardPage_w_News") ||
        node.Alias.InvariantEquals("NG_USK_StandardPageChild") ||
        node.Alias.InvariantEquals("NG_USK_StandardPageChild_w_News")
        );

      // loopp through to check if the doctype has the property or add it otherwise:
      foreach (var doctype in siteContentDocTypes)
      {
        try
        {
          //Found it - go to next doctype
          if (doctype.PropertyTypeExists("NG_NEWS_DisplayWidget")) continue;

          var dataTypeService = Umbraco.Core.ApplicationContext.Current.Services.DataTypeService;
          IDataTypeDefinition[] dataTypeDefinitions = dataTypeService.GetAllDataTypeDefinitions().ToArray();
          var checkbox = dataTypeDefinitions.FirstOrDefault(p => p.PropertyEditorAlias == "Umbraco.Truefalse");

          doctype.AddPropertyType(new PropertyType(checkbox)
          {
            Name = "Display Latest News Widget",
            Alias = "NG_NEWS_DisplayWidget",
            Description = "[Optional] Show the two Latest News titles here with a link to each article.",
            Mandatory = false,
            SortOrder = 2
          }, "Sidebar");

          contentTypeService.Save(doctype); //save the new property to the doctype

        }
        catch (Exception err)
        {
          // Get stack trace for the exception with source file information
          var st = new StackTrace(err, true);
          // Get the top stack frame
          var frame = st.GetFrame(0);
          // Get the line number from the stack frame
          var line = frame.GetFileLineNumber();
          LogHelper.Warn(typeof(BootstrapLatestNews),
            "ERROR ON: AddLatestNewsToSiteDocTypes - " + doctype.Alias + " ~ " + err.Message + "[" + line + "]:" + st);
        }
      }
      //Grab hold of the content service this time
      var contentService = UmbracoContext.Current.Application.Services.ContentService;
      //Refresh the content tree so we don't have to do it manually
      contentService.RebuildXmlStructures();
      //Add this even to the logs for our records
      LogHelper.Info<BootstrapLatestNews>("LATEST NEWS MODULE INSTALLER: Home Node and children were just saved and the xml tree was rebuilt");

      return true;
    }
    catch (Exception err)
    {
      // Get stack trace for the exception with source file information
      var st = new StackTrace(err, true);
      // Get the top stack frame
      var frame = st.GetFrame(0);
      // Get the line number from the stack frame
      var line = frame.GetFileLineNumber();
      LogHelper.Warn(typeof(BootstrapLatestNews),
        "ERROR ON: AddLatestNewsToSiteDocTypes - " + err.Message + "[" + line + "]:" + st);
      return false;
    }
  }

Any thoughts?

is working on a reply...