System Namespace
Represents a null value.
This class is used to indicate the absence of a known value, typically in a database application.
In database applications, a null reference ( Nothing in Visual Basic ) object is a valid value for a field. This class differentiates between a null value ( a null object ) and an uninitialized value ( the DBNull.Value instance ). For example, a table can have records with uninitialized fields. By default, these uninitialized fields have the DBNull value.
This class is also used in COM Interop to distinguish between a VT_NULL variant, which is associated with a null object, and a VT_EMPTY variant, which is associated with the DBNull.Value instance.
DBNull is never equal to anything.
DBNull is a singleton class, which means only one instance of this class can exist. That sole instance is DBNull.Value.
Data intensive applications accessing SQL databases must use the System.Data.SqlTypes classes, which have inherent support for a null reference ( Nothing ) values.
Convert.DBNull Convert.IsDBNull System.Runtime.InteropServices.VarEnum System.Data.SqlTypes
