I have added a new property - a Umbraco.DropDown.Flexible to a doctype thats used for nested content. The site has hundreds of instances of this nested content so i need to create a routine that sets the new property based one of the other properties (the title textstring). I loop through the published content of these instances, then create a new object and save the nested content property using contentservice. However while i am able to save textstrings, i cannot save complex datatypes. One of the properties is a Umbraco.MultiUrlPicker, and i cannot manage to pass that back in to the object to be saved.

In the code below "columnType" is the new property, and "itemLink" is the Url Picker

var nestedContentValue = new JArray();
if (results != null && results.Any()) {
    foreach (var b in results) {
        var nestedContentItem = new JObject();
        nestedContentItem.Add("key", Guid.NewGuid().ToString());
        nestedContentItem.Add("ncContentTypeAlias", "resultItem");
        nestedContentItem.Add("itemTitle", b.GetPropertyValue<string>("itemTitle"));
        nestedContentItem.Add("columnType", "1335");
        nestedContentItem.Add("itemFilesizeText", b.GetPropertyValue<string>("itemFilesizeText"));
        nestedContentItem.Add("itemLink", JsonConvert.SerializeObject(b.GetProperty("itemLink")));
        nestedContentValue.Add(nestedContentItem);
    }
    var contentItem = cs.GetById(testnodeid);
    contentItem.SetValue("items", JsonConvert.SerializeObject(nestedContentValue));
    var saveresult = cs.SaveAndPublishWithStatus(contentItem);  
}

I have also tried the following approach, but this gave the same outcome: "itemLink" is not set

dynamic ncItem = new ExpandoObject();
var thelink = (IEnumerable<Link>)b.GetPropertyValue("itemLink");
((IDictionary<string, object>)ncItem).Add("name", "Some item name");
((IDictionary<string, object>)ncItem).Add("ncContentTypeAlias", "resultItem");
((IDictionary<string, object>)ncItem).Add("itemTitle", b.GetPropertyValue<string>("itemTitle") + " -@ ");
((IDictionary<string, object>)ncItem).Add("itemLink", thelink);
((IDictionary<string, object>)ncItem).Add("itemFilesizeText", b.GetPropertyValue<string>("itemFilesizeText"));
((IDictionary<string, object>)ncItem).Add("columnType", "1335");
ncItems.Add(ncItem);

Can anyone tell me the correct way to set these troublesome properties?