These events occur when the schemas are added to the collection. If an event handler is not provided, an System.Xml.Schema.XmlSchemaException is thrown on any validation errors where the ValidationEventArgs.Severity is XmlSeverityType.Error. To specify an event handler, define a callback function and add it to the ValidationEventHandler.
The System.Xml.Schema.XmlSchemaCollection class is obsolete in the .NET Framework version 2.0 and has been replaced by the System.Xml.Schema.XmlSchemaSet class.