Trace.WriteLineIf Method (Boolean, String)
Writes a message to the trace listeners in the Listeners collection if a condition is true.
Assembly: System (in System.dll)
Notes to Implementers:
You can minimize the performance penalty of instrumenting your application by using If...Then statements instead of using mySwitch.TraceError evaluates to false you do not call WriteLine. The second example always calls , even when mySwitch.TraceError is false and no tracing output is produced. This can result in unnecessary execution of arbitrarily complex code.statements. The following two code examples send the same debugging message. However, the first example is much faster when tracing is off, because if
if(mySwitch.TraceError) Trace.WriteLine("aNumber = " + aNumber + " out of range");
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. 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. 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.") End Sub
Available since 1.1