Hi,

1) You could define a class that contain the custom properties, and assign its instances to the Tag property of items. This is useful if you need the same properties attached to several item types. If you need them for just one type of items, e.g. ShapeNode, you could derive from it and add new properties to the class declaration.

2) You might save it to XML by calling diagram.SaveToXml() or SaveToString(StringFormat.Xml). If the properties are stored as Tag values, handle the SerializeTag event to add custom Xml element to the node element.

I hope that helps,
Stoyan