I am trying to figure out why I can't get a package install to work on Umbraco 4.5.2... The following code works on 4.6 BUT NOT on 4.5??

            var dt = DataTypeDefinition.GetDataTypeDefinition(textStringId);
            mt.AddPropertyType(dt, forumUserTwitterUrl, "Twitter Username");
            var prop = mt.getPropertyType(forumUserTwitterUrl);
            prop.Mandatory = false;
            prop.TabId = GetTabByCaption(mt, memberTabName).Id;
            prop.Save();

I get the following error...

Method not found: 'umbraco.cms.businesslogic.propertytype.PropertyType umbraco.cms.businesslogic.ContentType.AddPropertyType(umbraco.cms.businesslogic.datatype.DataTypeDefinition, System.String, System.String)'.

I have also noticed, this codeplex item

http://umbraco.codeplex.com/workitem/29872

Please can someone point me in the direction of what I should be using for a 4.5.2 Umbraco install if this method is not in it?? As I can find no documentation anywhere??

Anyone.... ???