In this example the appointments have an additional annotation in the form of a custom attribute.
Custom attributes are freeform strings that are not processed in any way.
To enable custom attributes first ensure that your underlying data source is set to retrieve the corresponding columns.
Then use the CustomAttributeNames property to list them, separated with commas.
For exampe: CustomAttributeNames="Annotations"
The advanced form offers basic support for manipulating attributes.
When EnableCustomAttributeEditing property is set to true, a text box is rendered for each attribute.
This feature is turned off by default.