Export (0) Print
Expand All

Trace.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("TRACE")>]
static member WriteIf : 
        condition:bool * 
        message:string * 
        category:string -> unit

Parameters

condition
Type: System.Boolean

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

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 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) 
    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 TraceLevel Verbose, 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. The second message is followed by a line terminator.

No code example is currently available or this language may not be supported.

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Show:
© 2014 Microsoft