How to create Schematic Attribute (ArcObject .Net api)

Question

I am writing an ArcCatalog(10.1) Addin(C#) for creating a schematic diagram template and Element Classes. Now I need to create some attributes such as OriginNode and ExtrimityNode for Link class, Constant and another field Attribute for other classes.

I have created the element classes like the following, could not manage to create a ISchematicElementClass emtClass = [ISchematicDataset].CreateSchematicElementClass(elmClassName, esriSchematicElementType.esriSchematicNodeType);

Element Class Object has a method CreateSchematicAttribute("NodeName", uid) but can not manage, how to work with that....

It is giving an error "Item not found in the collection"

Can someone help ....

Thanks Naym