Warn Method (String, String, Exception)

TraceContext.Warn Method (String, String, Exception)

Writes trace information to the trace log, including any user-defined categories, trace messages, and error information. All warnings appear in the log as red text.

Namespace:  System.Web
Assembly:  System.Web (in System.Web.dll)

Public Sub Warn ( _
	category As String, _
	message As String, _
	errorInfo As Exception _


Type: System.String
The trace category that receives the message.
Type: System.String
The trace message to write to the log.
Type: System.Exception
An Exception that contains information about the error.

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 the ErrorInfo property is set to the object passed by the errorInfo parameter.

The following code example demonstrates how to call the Write method to write an error trace message to the trace log. In this example, different exceptions are traced as errors and warnings. When the page throws an ArgumentException, it writes a warning message using the Warn method. When the page throws an InvalidOperationException, it writes an error message using the Write method.

<%@ Page language="VB" Trace="true" %>
<script runat="server">
' The Page_Load method.
Private Sub Page_Load(sender As Object, e As EventArgs)

    ' Register a handler for the TraceFinished event.
    AddHandler Trace.TraceFinished, AddressOf OnTraceFinished

	Dim ae As New ArgumentException("Trace Test")
        Throw ae

    catch ioe As InvalidOperationException
        ' You can write an error trace message using the Write method.
        Trace.Write("Exception Handling", "Exception: Page_Load.", ioe)

    Catch ae As ArgumentException
        ' You can write a warning trace message using the Warn method.
        Trace.Warn("Exception Handling", "Warning: Page_Load.", ae)

    End Try

End Sub ' Page_Load

' A TraceContextEventHandler for the TraceFinished event.
Private Sub OnTraceFinished(sender As Object, e As TraceContextEventArgs)

    Dim r As TraceContextRecord
    Dim o As Object

    ' Iterate through the collection of trace records and write 
    ' them to the response stream.

    For Each o In e.TraceRecords
        r = CType(o, TraceContextRecord)
	If r.IsWarning Then
            Response.Write(String.Format("warning message: {0} <BR>", r.Message))
            Response.Write(String.Format("error message: {0} <BR>", r.Message))
        End If

End Sub	' OnTraceFinished

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, 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.

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