WriteIf Method (Boolean, String, String)
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Debug.WriteIf Method (Boolean, String, String)

 

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

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

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

Parameters

condition
Type: System.Boolean

The conditional expression to evaluate. If the condition is true, the category name and message are written to the trace listeners in the collection.

message
Type: System.String

A message to write.

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 TraceListener.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:

if(mySwitch.TraceError) 
    Debug.Write("aNumber = " + aNumber + " out of range");

Second example:

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

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

If the switch is set to the TraceLevelVerbose, 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 Error or higher, the example outputs the second error message on the same line as the first message. A line terminator follows the second message.

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

 static public void MyErrorMethod(Object myObject, String category) {
    // Write the message if the TraceSwitch level is set to Verbose.
    Debug.WriteIf(generalSwitch.TraceVerbose, myObject.ToString() + 
       " is not a valid object for category: ", category);

    // Write a second message if the TraceSwitch level is set to Error or higher.
    Debug.WriteLineIf(generalSwitch.TraceError, " Please use a different category.");
 }

Universal Windows Platform
Available since 10
.NET Framework
Available since 1.1
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