By default, the Key property is empty. A category-axis can be referred by its index or by its key. The Index property returns the index of the category-axis (0-based). The Add method adds a CategoryAxis object to the collection and returns a reference to the newly created object. The Remove method removes a specific member from the CategoryAxes collection, giving its identifier. The Clear method Removes all objects in the collection. The Item property accesses a category-axis giving its index or key.