Checks whether the current table instance is valid and usable.
The Validate method throws an exception if the current table is marked as deleted and is therefore unusable.
Table tbl = RichEditControl.Document.Tables;
Subsequently, at some point the table may be deleted and the reference becomes invalid. Even when a table is restored with Undo, the table is re-created as a new object and the former reference becomes unusable. When this happens, the Validate method will throw an exception.