Introduction

Tracing mechanism in Windows Communication Foundation is based on the classes that reside in System.Diagnostic namespace. Important classes are Trace, TraceSource and TraceListener.

Following are the steps to enable tracing in WCF:

Configuring WCF to emit tracing information/Define Trace Source, we have the following options:

System.ServiceModel
System.ServiceModel.MessageLogging
System.ServiceModel.IdentityModel
System.ServiceModel.Activation
System.Runtime.Serialization
System.IO.Log
Cardspace

In configuration file, we will define a source to enable this configuration as follows:

<source name="System.ServiceModel.MessageLogging">

Setting Tracing Level, we have the following available options, we need to set this tracing level to available options other than default "Off":

Off
Critical
Error
Warning
Information
Verbose
ActivityTracing
All

In configuration file, we can choose the above values for switchValue attribute as follows:

<source name="System.ServiceModel.MessageLogging"
                               switchValue="Information">

Configuring a trace listener:

For configuring a trace listener, we will add the following to config file.

<listeners>
    <add name="messages"
            type="System.Diagnostics.XmlWriterTraceListener"
            initializeData="d:\logs\messages.svclog" />
</listeners>

Enabling message logging:
```
      <system.serviceModel>
         <diagnostics>
            <messageLogging 
                    logEntireMessage="true" 
                    logMalformedMessages="false"
                    logMessagesAtServiceLevel="true" 
                    logMessagesAtTransportLevel="false"
                    maxMessagesToLog="3000"
                    maxSizeOfMessageToLog="2000"/>
         </diagnostics>
       </system.serviceModel>
```
- logEntireMessage: By default, only the message header is logged but if we set it to true, the entire message including message header as well as body will be logged.
- logMalformedMessages: This option logs messages that are rejected by WCF stack at any stage known as malformed messages.
- logMessagesAtServiceLevel: Messages those are about to enter or leave user.
- logMessagesAtTransportLevel: Messages those are about to encode or decode.
- maxMessagesToLog: Maximum quota for messages. Default value is 10000.
- maxSizeOfMessageToLog: Message size in bytes.

Finally, putting all this together, the configuration file will appear like this:

 <system.diagnostics> 
   <sources>
      <source name="System.ServiceModel.MessageLogging">
        <listeners>
          <add name="messagelistener"
               type="System.Diagnostics.XmlWriterTraceListener" 
                      initializeData="d:\logs\myMessages.svclog"></add>
        </listeners>
      </source>
    </sources>
  </system.diagnostics> 
  <system.serviceModel>       
      <diagnostics>
        <messageLogging logEntireMessage="true"
                        logMessagesAtServiceLevel="false"
                        logMessagesAtTransportLevel="false"
                        logMalformedMessages="true"
                        maxMessagesToLog="5000"
                        maxSizeOfMessageToLog="2000">         
        </messageLogging>
      </diagnostics>
  </system.serviceModel>

Note: In this case, information will be buffered and not published to file automatically. So, we can set the autoflush property of the trace under sources as follows:

<trace autoflush ="true" />

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Simple Steps to Enable Tracing in WCF