Specifies a static value that is used by the WPF property system rather than null to indicate that the property exists, but does not have its value set by the property system.
Assembly: WindowsBase (in WindowsBase.dll)
is a sentinel value that is used for scenarios where the WPF property system is unable to determine a requested DependencyProperty value. is used rather than null, because null could be a valid property value, as well as a valid (and frequently used) DefaultValue.
A dependency property has a default value established in metadata and that value is returned. This value might come from DefaultMetadata.
Some other value was established by the property system, and the default value is no longer relevant. For details, see Dependency Property Value Precedence.
Setting a DefaultValue of is specifically disallowed.
DependencyObject.ReadLocalValue returns when the requested property has not been locally set.
Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.