[CONNECT C#] add custom property type to item type array property.

i have an item type that contains a property. this property has Is Array set to true and its type is a custom property type that i made.

trying to figure out how to add a value to this array property. 

Not seeing it in the sdk. i see there is a XmlStringValue that is a get/set. but when i try to set it, it just crashes. assuming i cant use that to add a new value to an array but could use it to change existing values??

Anyways anyone see a way to do this. i hope im just missing it.

EDIT:

adding some code that i have, the array property is named Values, the custom type is named linker. the custom type contains several string properties...

            CustomItemHost host = new CustomItemHost(Views.LinkSetup._MainWindowViewModel.selTextElement, false);
            IList<BD.DgnEC.IDgnECInstance> ItemTypes = host.CustomItems;
            //loop each itemtype attached to element
            foreach (BD.DgnEC.IDgnECInstance curItemType in ItemTypes)
            {
                //find item type with specfied name
                if (curItemType.ClassDefinition.Name.ToUpper().Contains(Globals.itemTypeName.ToUpper()))
                {//found, update
                    //find array property (its named Values)
                    foreach (var curprop in curItemType)
                    {
                        if (curprop.Property.DisplayLabel.ToUpper() == "VALUES")
                        {
                            //add entry to values array
                            //stuck on how to do this..
                            //try and modify xml string to add another value to the VALUES propety (which is a custom propety tyoe named linker)
                            string newxmlstring = curprop.XmlStringValue;
                            newxmlstring.Replace("</Values>", "");
                            newxmlstring += "<linker><isFromReference>False</isFromReference><ElementID>5</ElementID><ModelName>f</ModelName><PropertyName>df</PropertyName><FilePath>test2</FilePath><PropertyType>Element</PropertyType><PropertyValue>df</PropertyValue><AccessString>afsdfdfasf</AccessString><ItemTypeName /></linker></Values>";
                            //causes crash
                            curprop.XmlStringValue = newxmlstring;
                        }
                    }
                }

            }

i was thinking i would need to get the custom property type and populate it with what i want, then add it as a value to the item type property. but see nothing in the SDK for this...i starting to do this to get the property type...

BD.ItemTypeLibrary OHDOTLinkersLib = BD.ItemTypeLibrary.FindByName(Globals.itemTypeLibName, activeFile);
BD.ItemType it_TextFieldLinker = OHDOTLinkersLib.GetItemTypeByName(Globals.itemTypeName);
BD.CustomProperty itProp = it_TextFieldLinker.GetPropertyByName("Values");
BD.CustomPropertyType itPropType = OHDOTLinkersLib.GetCustomTypeByName("linker");