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Logging sample

Shows how to use the Logging APIs in the Windows.Foundation.Diagnostics namespace, including LoggingChannel, LoggingActivity, LoggingSession, and FileLoggingSession. These classes are designed for diagnostic logging within a modern application.

Note: This sample is part of a large collection of UWP feature samples. If you are unfamiliar with Git and GitHub, you can download the entire collection as a ZIP file, but be sure to unzip everything to access shared dependencies. For more info on working with the ZIP file, the samples collection, and GitHub, see Get the UWP samples from GitHub. For more samples, see the Samples portal on the Windows Dev Center.

These APIs were added in Windows 8.1. The LoggingChannel and LoggingActivity APIs have been extended in Windows 10 to support writing complex events using TraceLogging event encoding.

  • LoggingChannel: The LoggingChannel class is used to generate events. The core LoggingChannel APIs can create simple events - events with a name and a string value, or events with a name, a string value, and an integer value. Starting with Windows 10, the LoggingChannel class can use TraceLogging event encoding to create complex events with arbitrary structured data.
  • LoggingActivity: The LoggingActivity class is used to encapsulate an activity by writing a Start event when the activity is created and a Stop event when the activity is closed. Starting with Windows 10, the LoggingActivity class can use TraceLogging event encoding to write complex events associated with the activity and to support nested activities.
  • LoggingSession: The LoggingSession class captures events into an in-memory circular buffer with the ability to save the buffer contents to a log file on-demand.
  • FileLoggingSession: The FileLoggingSession class captures events directly to a sequence of log files, switching to a new log file when the maximum file size is reached.

The Logging classes are based on Windows ETW APIs. Events from these classes can be captured using ETW tools such as xperf. The log files are generated in ETL format so they can be viewed and processed by the Windows Performance Toolkit (WPT), as well as utilities such as tracerpt.exe or xperf.exe.

Note The Windows universal samples require Visual Studio 2017 to build and Windows 10 to execute.

To obtain information about Windows 10 development, go to the Windows Dev Center

To obtain information about Microsoft Visual Studio and the tools for developing Windows apps, go to Visual Studio

How to capture logging output

You can collect the events generated by the logging classes with xperf or another ETL controller tool. To collect these events in an ETL file, first start the capture session by running the command

xperf -start MySession -f MyFile.etl -on Id

where the Id is given below.

Next, run the sample and run the appropriate scenario.

When done, run the command

xperf -stop MySession

After collecting the ETL file, you can decode the trace using xperf, wpa, or tracerpt. For example, to decode MyFile.etl with tracerpt, run the command

tracerpt MyFile.etl

This generates the file dumpfile.xml.

Note that decoding TraceLogging events requires Windows 10. Earlier versions of Windows can only reliably decode the simple (manifest-based) events.

Windows 8.1 style events

If you use the LoggingChannel class's one-parameter constructor, the result is a Windows 8.1-style logging channel.

  • The channel's ETW Id is 4bd2826e-54a1-4ba9-bf63-92b73ea1ac4a
  • The channel's ETW Name is Microsoft-Windows-Diagnostics-LoggingChannel
  • A LoggingChannelName field containing the Channel Name is automatically added to each event.
  • Simple events will be written using manifested-event encoding.

Therefore, you would use the command line

xperf -start MySession -f MyFile.etl -on 4bd2826e-54a1-4ba9-bf63-92b73ea1ac4a

to start capturing events with xperf.

Note that complex events can be written even when using Windows 8.1 mode. Complex events always use TraceLogging encoding.

The 1-parameter constructor is marked as obsolete to ensure that developers are aware of the changes in semantics. The Windows 10 semantics are useful because they enable use of the ETW Provider Id for event filtering.

Windows 10 style events

If you use the LoggingChannel class's two-parameter or three-parameter constructor, the result is a Windows 10-style logging channel.

  • The channel's ETW Id is specified by the third constructor parameter, if present; otherwise it is generated from the Channel Name by the same hashing algorithm as the .NET EventSource class.
  • The channel's ETW Name is specified by the first constructor parameter.

In the sample, the channel name is "SampleProvider", which hashes to eff1e128-4903-5093-096a-bdc29b38456f.

Therefore, you would use the command line

xperf -start MySession -f MyFile.etl -on eff1e128-4903-5093-096a-bdc29b38456f

to start capturing events with xperf.

xperf version 10.0.16299 and higher support specifying the channel name with a leading asterisk:

xperf -start MySession -f MyFile.etl -on *SampleProvider

Related topics


Logging Sample


Windows Performance Toolkit

System requirements

Client: Windows 10

Server: Windows Server 2016 Technical Preview

Phone: Windows 10

Build the sample

  1. If you download the samples ZIP, be sure to unzip the entire archive, not just the folder with the sample you want to build.
  2. Start Microsoft Visual Studio 2017 and select File > Open > Project/Solution.
  3. Starting in the folder where you unzipped the samples, go to the Samples subfolder, then the subfolder for this specific sample, then the subfolder for your preferred language (C++, C#, or JavaScript). Double-click the Visual Studio Solution (.sln) file.
  4. Press Ctrl+Shift+B, or select Build > Build Solution.

Run the sample

The next steps depend on whether you just want to deploy the sample or you want to both deploy and run it.

Deploying the sample

  • Select Build > Deploy Solution.

Deploying and running the sample

  • To debug the sample and then run it, press F5 or select Debug > Start Debugging. To run the sample without debugging, press Ctrl+F5 or selectDebug > Start Without Debugging.
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