Parent-child hierarchy

Doc objects are part of a parent-child containment hierarchy, where the parent represents the container and the children represent the contents. If a doc object is deleted, all its descendants (its children, recursively) are also deleted.

For example, a Part contains zero or more DesignBody objects, each of which contains one or more DesignFace objects. The parent of a design face is a design body, and the parent of a design body is a part. Similarly, a design body is a child of a part, and a design face is a child of a design body.

Public static void Example(DesignBody desBody) {
	Part part = desBody.Parent;

	// a part is a root object, so it has no parent
	Debug.Assert(part.Parent == null);
	Debug.Assert(part.Root == part);

	// GetChildren<T> returns immediate children of type T
	foreach (DocObject child in part.GetChildren<DocObject>()) {
		// Parent returns the immediate parent
		Debug.Assert(child.Parent == part);
	}

	// DesignBody.Faces is equivalent to GetChildren<DesignFace>
	foreach (DesignFace desFace in desBody.Faces) {
		// Root returns the topmost parent
		Debug.Assert(desFace.Root == part);
	}

	// GetDescendants<T> gets all nested children of type T
    // the search starts with the object itself
	foreach (DesignFace desFace in part.GetDescendants<DesignFace>()) {
		// GetAncestor<T> crawls up the parent chain to find an object of type T
		Debug.Assert(desFace.GetAncestor<Part>() == part);

		// the search starts with the object itself
		Debug.Assert(desFace.GetAncestor<DesignFace>() == desFace);
	}
}

The parent chain continues up the hierarchy until the root object is reached. This is the topmost parent, which itself has no parent (its parent is null). Examples of root objects are: Part, DrawingSheet, and Layer.

All doc objects in the same parent-child hierarchy belong to the same document. The Document class provides properties to access its root objects: MainPart, Parts, DrawingSheets, and Layers.