Reduces the expression to a known node type (that is not an Extension node) or just returns the expression if it is already a known type.
Assembly: System.Core (in System.Core.dll)
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.