Trace.WriteIf 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)

static void WriteIf (
	bool condition, 
	Object^ value, 
	String^ category
/** @attribute ConditionalAttribute("TRACE") */ 
public static void WriteIf (
	boolean condition, 
	Object value, 
	String category
public static function WriteIf (
	condition : boolean, 
	value : Object, 
	category : String
Not applicable.



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


An Object whose name is sent to the Listeners.


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 Write 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 WriteIf 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 Write. The second example always calls WriteIf, even when mySwitch.TraceError is false and no tracing output is produced. This can result in unnecessary execution of arbitrarily complex code. First example

    Trace.Write("aNumber = " + aNumber + " out of range");
Second example
Trace.WriteIf(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 TraceLevelVerbose, the example outputs the name of the myObject and the category to the Listeners. For information on adding a listener to the Listeners collection, see the TraceListenerCollection class.

Then, if the TraceLevel is set to Error or higher, 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 = 
      gcnew TraceSwitch( "General", "Entire Application" );

   static void MyErrorMethod( Object^ myObject, String^ category )
      #if defined(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." );

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

public static void MyErrorMethod(Object myObject, String category)
    // Write the message if the TraceSwitch level is set to Verbose.
    Trace.WriteIf(generalSwitch.get_TraceVerbose(), myObject, category);

    // Write a second message if the TraceSwitch level is set to Error
    // or higher.         
         " Object is not valid for this category.");
} //MyErrorMethod

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

function MyErrorMethod(myObject : Object, category : String)
   // 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.
      " Object is not valid for this category.")

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

Community Additions