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Trace.WriteLineIf Method (Boolean, Object, String)

Writes a category name and the value of the object's ToString method to the trace listeners in the Listeners collection if a condition is true.

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

public static function WriteLineIf(
	condition : boolean, 
	value : Object, 
	category : String
)

Parameters

condition
Type: System.Boolean

true to cause a message to be written; otherwise, false.

value
Type: System.Object

An Object whose name is sent to the Listeners.

category
Type: System.String

A category name used to organize the output.

By default, the output is written to an instance of DefaultTraceListener.

The category parameter can be used to group output messages.

This method calls the WriteLine method of the trace listener.

Notes to Implementers:

You can minimize the performance penalty of instrumenting your application by using If...Then statements instead of using WriteLineIf statements. The following two code examples send the same debugging message. However, the first example is much faster when tracing is off, because if mySwitch.TraceError evaluates to false you do not call WriteLine. The second example always calls WriteLineIf, even when mySwitch.TraceError is false and no tracing output is produced. This can result in unnecessary execution of arbitrarily complex code.

First example

if(mySwitch.TraceError) 
    Trace.WriteLine("aNumber = " + aNumber + " out of range");

Second example

Trace.WriteLineIf(mySwitch.TraceError, "aNumber = " + aNumber + " out of range");

The following example creates a TraceSwitch named generalSwitch. This switch is set outside the code sample.

If the switch is set to the TraceLevel Error or higher, the example outputs the first error message to the Listeners. For information on adding a listener to the Listeners collection, see the TraceListenerCollection class.

Then, if the TraceLevel is set to Verbose, the example outputs the second error message on the same line as the first message. The second message is followed by a line terminator.

// Create a TraceSwitch.
var generalSwitch : TraceSwitch = 
   new TraceSwitch("General", "Entire Application")    

function MyErrorMethod(myObject : Object, category : String)
{
   @if(@TRACE)
   // Write the message if the TraceSwitch level is set to Verbose.
   Trace.WriteIf(generalSwitch.TraceVerbose, myObject, category)

   // Write a second message if the TraceSwitch level is set
   // to Error or higher.
   Trace.WriteLineIf(generalSwitch.TraceError, 
      " Object is not valid for this category.")
   @end
}

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, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

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, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5

XNA Framework

Supported in: 3.0, 2.0, 1.0

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