PropertyCollection props = Constraint.ExtendedProperties;
Contains a PropertyCollection that can store any amount of miscellaneous information about the Constraint . The information in the ExtendedProperties collection is for use by your code only; it isn't used by the .NET framework.
The ProperyCollection is derived from the Hashtable class. Most disconnected data objects provide an ExtendedProperties collection, including the DataSet , DataColumn , DataTable , and DataRelation classes.
The following code snippet stores the name of a DataRelation object that relates to a ForeignKeyConstraint :
fkc.ExtendedProperties["RelationName"] = dr.RelationName;
Items in the PropertyCollection must be strings if you want them to persist when the DataSet is written to XML.