Debug.WriteLineIf Method (Boolean, String) (System.Diagnostics)

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.NET Framework Class Library

Debug.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)

Syntax

Visual Basic

<ConditionalAttribute("DEBUG")> _
Public Shared Sub WriteLineIf ( _
	condition As Boolean, _
	message As String _
)

[ConditionalAttribute("DEBUG")]
public static void WriteLineIf(
	bool condition,
	string message
)

Visual C++

[ConditionalAttribute(L"DEBUG")]
public:
static void WriteLineIf(
	bool condition, 
	String^ message
)

[<ConditionalAttribute("DEBUG")>]
static member WriteLineIf : 
        condition:bool * 
        message:string -> unit

Parameters

condition: Type: System.Boolean
The conditional expression to evaluate. If the condition is true, the message is written to the trace listeners in the collection.

message: Type: System.String
A message to write.

Remarks

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

This method calls the TraceListener.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) 
     Debug.WriteLine("aNumber = " + aNumber + " out of range");

Second example:

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

Examples

The following example creates a TraceSwitch named generalSwitch. This switch is set outside of 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 about 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. A line terminator follows the second message.

Visual Basic


' Class-level declaration.
' Create a TraceSwitch.
Private Shared generalSwitch As New TraceSwitch("General", "Entire Application")


Public Shared Sub MyErrorMethod()
    ' Write the message if the TraceSwitch level is set to Error or higher.
    Debug.WriteIf(generalSwitch.TraceError, "My error message. ")

    ' Write a second message if the TraceSwitch level is set to Verbose.
    Debug.WriteLineIf(generalSwitch.TraceVerbose, "My second error message.")
End Sub 'MyErrorMethod


// 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.
    Debug.WriteIf(generalSwitch.TraceError, "My error message. ");

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

Visual C++


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

public:
   static void MyErrorMethod()
   {
      // Write the message if the TraceSwitch level is set to Error or higher.
      #if defined(DEBUG)
      Debug::WriteIf( generalSwitch->TraceError, "My error message. " );

      // Write a second message if the TraceSwitch level is set to Verbose.
      Debug::WriteLineIf( generalSwitch->TraceVerbose, 
         "My second error message." );
      #endif
   }

Version Information

.NET Framework

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

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Platforms

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.

Reference

Debug Class

WriteLineIf Overload

System.Diagnostics Namespace

Debug

Trace

BooleanSwitch

TraceSwitch

TraceListener

DefaultTraceListener

ConsoleTraceListener

ConditionalAttribute