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Trace.WriteLineIf Method (Boolean, String)

Writes a message to the trace listeners in the Listeners collection if a condition is true.

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

[ConditionalAttribute("TRACE")] 
public static void WriteLineIf (
	bool condition,
	string message
)
/** @attribute ConditionalAttribute("TRACE") */ 
public static void WriteLineIf (
	boolean condition, 
	String message
)
ConditionalAttribute("TRACE") 
public static function WriteLineIf (
	condition : boolean, 
	message : String
)
Not applicable.

Parameters

condition

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

message

A message to write.

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

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 TraceLevelError 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.

// Class-level declaration.
 // Create a TraceSwitch.
 static TraceSwitch generalSwitch = new TraceSwitch("General", "Entire Application");
 
 static public void MyErrorMethod() {
    // Write the message if the TraceSwitch level is set to Error or higher.
    Trace.WriteIf(generalSwitch.TraceError, "My error message. ");
 
    // Write a second message if the TraceSwitch level is set to Verbose.
    Trace.WriteLineIf(generalSwitch.TraceVerbose, "My second error message.");
 }


// Class-level declaration.
// Create a TraceSwitch.
private static TraceSwitch generalSwitch = 
    new TraceSwitch("General", "Entire Application");

public static void MyErrorMethod()
{
    // Write the message if the TraceSwitch level is set to Error or higher.
    Trace.WriteIf(generalSwitch.get_TraceError(), "My error message. ");

    // Write a second message if the TraceSwitch level is set to Verbose.
    Trace.WriteLineIf(generalSwitch.get_TraceVerbose(),
         "My second error message.");
} //MyErrorMethod

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

function MyErrorMethod()
{
   @if(@TRACE)
   // Write the message if the TraceSwitch level is set to
   // Error or higher.
   Trace.WriteIf(generalSwitch.TraceError, "My error message. ");
 
   //Write a second message if the TraceSwitch level is set to Verbose.
   Trace.WriteIf(generalSwitch.TraceVerbose, "My second error message.");
   @end
}

Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

XNA Framework

Supported in: 1.0

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