【ORD c#】获取参数化单元的itemtype属性值

老师好，我现在加载一个.cel格式的文件，获取如图所示，我使用了如下代码获取不出来

 CustomItemHost host = new CustomItemHost(dgnfile);
                IDgnECInstance item = host.GetCustomItem("端横梁", "端横梁");
                Bentley.DgnPlatformNET.ItemTypeLibrary itemTypeLibrary = Bentley.DgnPlatformNET.ItemTypeLibrary.FindByName("小箱梁", dgnfile);
                Bentley.DgnPlatformNET.ItemType itemType = itemTypeLibrary.GetItemTypeByName("端横梁");
                CustomProperty property = itemType.GetPropertyByName("梁高");
                string internalName = property.InternalName;
                IECPropertyValue val = item.GetPropertyValue(internalName);
                MessageBox.Show(val != null ? val.StringValue : "val==null");