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C# in a Nutshell, Second Edition
book

C# in a Nutshell, Second Edition

by Peter Drayton, Ben Albahari, Ted Neward
August 2003
Intermediate to advanced content levelIntermediate to advanced
928 pages
32h 1m
English
O'Reilly Media, Inc.
Content preview from C# in a Nutshell, Second Edition

Name

DBNull

Synopsis

DBNull indicates the absence of information, typically in a database application in which a field does not contain any data. The types in the System.Data.SqlTypes namespace have built-in support for DBNull.

Note that Value is not the same as the null keyword in C#. The null keyword can be used to release an object by clearing the reference. System.DBNull.Value, on the other hand, is a reference to a special value (a member of the singleton class DBNull) that is used to indicate missing information.

This class has some other uses, namely in COM Interop, in which it represents a VT_EMPTY variant (as opposed to a VT_NULL variant, which is a null reference).

public sealed class DBNull : System.Runtime.Serialization.ISerializable, IConvertible {
// Public Static Fields
   public static readonly DBNull Value;
// Public Instance Methods
   public void GetObjectData(System.Runtime.Serialization.SerializationInfo info,
        System.Runtime.Serialization.StreamingContext context)
// implements ISerializable
   public TypeCode GetTypeCode( );        
// implements IConvertible
   public override string ToString( );    
// overrides object
   public string ToString(IFormatProvider provider); 
// implements IConvertible
}
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Publisher Resources

ISBN: 0596005261Catalog PageErrata