This exception is thrown when you try to access a null value in a column of a strongly typed DataSet . This exception isn't generated by the .NET runtime. Instead, the strongly typed DataSet class catches an System.InvalidCastException and then throws a StrongTypingException to notify your code of the problem. This code takes place in the get property accessor for a strongly typed DataRow . public class StrongTypingException : DataException { // Public Constructors public StrongTypingException ( ); public StrongTypingException (string s , Exception innerException ); // Protected Constructors protected StrongTypingException (System.Runtime.Serialization.SerializationInfo info , System.Runtime.Serialization.StreamingContext context ); } HierarchySystem.Object System.Exception(System.Runtime.Serialization.ISerializable) System.SystemException DataException StrongTypingException |