TraceContext.Warn Method (String, String)
Writes trace information to the trace log, including any user-defined categories and trace messages. All warnings appear in the log as red text.
Assembly: System.Web (in System.Web.dll)
Every time the Warn method is called, a TraceContext trace message is added to the TraceRecords messages collection, which is accessible when you handle the TraceFinished event. The message is added with its IsWarning property set to true and its ErrorInfo property set to a null reference (Nothing in Visual Basic).
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.