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OptionalFieldAttribute Class

Specifies that a field can be missing from a serialization stream so that the BinaryFormatter and the SoapFormatter does not throw an exception.

Namespace:  System.Runtime.Serialization
Assembly:  mscorlib (in mscorlib.dll)

[AttributeUsageAttribute(AttributeTargets.Field, Inherited = false)]
public sealed class OptionalFieldAttribute : Attribute

This attribute allows you to specify that new fields in a serializable type (a type to which the SerializableAttribute is applied to) are ignored by the BinaryFormatter or the SoapFormatter. This enables version-tolerant serialization of types created for older versions of an application that serializes data. For example, when the formatters encounter a stream produced by a version that does not include the new fields, no exception is thrown, and the existing data on the older type is processed as normal.


Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0