This class is accessed using the ExtendedProperties property of the DataColumn , DataTable , DataSet , Constraint , and DataRelation . It can store additional information about the object. For example, you might want to store an expiration date for a DataSet . public class PropertyCollection : Hashtable { // Public Constructors public PropertyCollection ( ); } HierarchySystem.Object System.Collections.Hashtable(System.Collections.IDictionary, System.Collections.ICollection , System.Collections.IEnumerable , System.Runtime.Serialization.ISerializable , System.Runtime.Serialization.IDeserializationCallback , System.ICloneable) PropertyCollection Returned ByConstraint.ExtendedProperties , DataColumn.ExtendedProperties , DataRelation.ExtendedProperties , DataSet.ExtendedProperties , DataTable.ExtendedProperties |