Provides an example of processing a YAML file containing evidence for device detection.There are 20,000 examples in the supplied file of evidence representing HTTP Headers. For example:
header.user-agent: 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/98.0.4758.102 Safari/537.36'
header.sec-ch-ua: '" Not A;Brand";v="99", "Chromium";v="98", "Google Chrome";v="98"'
header.sec-ch-ua-full-version: '"98.0.4758.87"'
header.sec-ch-ua-mobile: '?0'
header.sec-ch-ua-platform: '"Android"'
We create a device detection pipeline to read the data and find out about the associated device, we write this data to a YAML formatted output stream.
As well as explaining the basic operation of off line processing using the defaults, for advanced operation this example can be used to experiment with tuning device detection for performance and predictive power using Performance Profile, Graph and Difference and Drift settings.
This example is available in full on GitHub.
This example requires a local data file. The free 'Lite' data file can be acquired by pulling the git submodules under this repository (run `git submodule update --recursive`) or from the device-detection-data GitHub repository.
The Lite data file is only used for illustration, and has limited accuracy and capabilities. Find out about the more capable data files that are available on our pricing page
Required NuGet Dependencies:
- FiftyOne.DeviceDetection
- Microsoft.Extensions.Logging.Console
- YamlDotNet
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* Copyright 2025 51 Degrees Mobile Experts Limited, Davidson House,
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using FiftyOne.Pipeline.Core.FlowElements;
using FiftyOne.Pipeline.Engines;
using Microsoft.Extensions.Logging;
using System.Collections.Generic;
using System.IO;
using YamlDotNet.Serialization;
{
public class Program
{
public class Example : ExampleBase
{
string dataFile,
TextReader evidenceYaml,
ILoggerFactory loggerFactory,
TextWriter output)
{
var logger = loggerFactory.CreateLogger<Program>();
// In this example, we use the DeviceDetectionPipelineBuilder and configure it
// in code. For more information about builders in general see the documentation at
// https://51degrees.com/documentation/_concepts__configuration__builders__index.html
// Note that we wrap the creation of a pipeline in a using to control its life cycle
using (var pipeline = new DeviceDetectionPipelineBuilder(loggerFactory)
.UseOnPremise(dataFile, null, false)
// We use the low memory profile as its performance is sufficient for this
// example. See the documentation for more detail on this and other
// configuration options:
// https://51degrees.com/documentation/_device_detection__features__performance_options.html
// https://51degrees.com/documentation/_features__automatic_datafile_updates.html
// https://51degrees.com/documentation/_features__usage_sharing.html
.SetPerformanceProfile(PerformanceProfiles.LowMemory)
// Inhibit sharing usage for this example.
// In general, off line processing usage should NOT be shared back to 51Degrees.
// This is because it will not contain the full set of information that is
// required by our data processing back-end and will be discarded.
// If you specifically want to share data that is being processed off line
// in order to help us improve detection of new devices/browsers/etc, then
// this additional data will need to be collected and included as evidence
// to the Pipeline. See
// https://51degrees.com/documentation/_features__usage_sharing.html#Low_Level_Usage_Sharing
// for more details on this.
.SetShareUsage(false)
// Inhibit auto-update of the data file for this example
.SetAutoUpdate(false)
.SetDataUpdateOnStartUp(false)
.SetDataFileSystemWatcher(false)
.Build())
{
var serializer = new Serializer();
{
// write the yaml document separator
output.WriteLine("---");
// Pass the record to the pipeline as evidence so that it can be analyzed
AnalyseEvidence(evidence, pipeline, output, serializer);
}
// write the yaml document end marker
output.WriteLine("...");
ExampleUtils.CheckDataFile(pipeline, loggerFactory.CreateLogger<Program>());
}
}
private void AnalyseEvidence(
Dictionary<string, object> evidence,
IPipeline pipeline,
TextWriter writer,
Serializer serializer)
{
// FlowData is a data structure that is used to convey information required for
// detection and the results of the detection through the pipeline.
// Information required for detection is called "evidence" and usually consists
// of a number of HTTP Header field values, in this case represented by a
// Dictionary<string, object> of header name/value entries.
//
// FlowData is wrapped in a using block in order to ensure that the unmanaged
// resources allocated by the native device detection library are freed
using (var data = pipeline.CreateFlowData())
{
// Add the evidence values to the flow data
data.AddEvidence(evidence);
// Process the flow data.
data.Process();
var device = data.Get<IDeviceData>();
Dictionary<string, string> output = new Dictionary<string, string>();
// Add the evidence values to the output
foreach(var entry in evidence)
{
output.Add(entry.Key, entry.Value.ToString());
}
// Now add the values that we want to store against the record.
output.Add("device.ismobile", device.IsMobile.HasValue ?
device.IsMobile.Value.ToString() : "Unknown");
output.Add("device.platformname", device.PlatformName.GetHumanReadable());
output.Add("device.platformversion", device.PlatformVersion.GetHumanReadable());
output.Add("device.browsername", device.BrowserName.GetHumanReadable());
output.Add("device.browserversion", device.BrowserVersion.GetHumanReadable());
// DeviceId is a unique identifier for the combination of hardware, operating
// system, browser and crawler that has been detected.
// Our device detection solution uses machine learning to find the optimal
// way to identify devices based on the real-world evidence values that we
// observe each day.
// As this changes over time, the result of detection can potentially change
// as well. By storing the device id, we can use this as a lookup in future
// rather than performing detection with the original evidence again.
// Do this by passing an evidence entry with:
// key = query.51D_ProfileIds
// value = [the device id]
// This is much faster and avoids the potential for getting a different
// result.
output.Add("device.deviceid", device.DeviceId.GetHumanReadable());
serializer.Serialize(writer, output);
}
}
}
static void Main(string[] args)
{
// Use the supplied path for the data file or find the lite file that is included
// in the repository.
var dataFile = args.Length > 0 ? args[0] :
// In this example, by default, the 51degrees "Lite" file needs to be somewhere in the
// project space, or you may specify another file as a command line parameter.
//
// Note that the Lite data file is only used for illustration, and has limited accuracy
// and capabilities. Find out about the Enterprise data file on our pricing page:
// https://51degrees.com/pricing
ExampleUtils.FindFile(Constants.LITE_HASH_DATA_FILE_NAME);
// Do the same for the yaml evidence file.
var evidenceFile = args.Length > 1 ? args[1] :
// This file contains the 20,000 most commonly seen combinations of header values
// that are relevant to device detection. For example, User-Agent and UA-CH headers.
ExampleUtils.FindFile(Constants.YAML_EVIDENCE_FILE_NAME);
// Finally, get the location for the output file. Use the same location as the
// evidence if a path is not supplied on the command line.
var outputFile = args.Length > 2 ? args[2] :
Path.Combine(Path.GetDirectoryName(evidenceFile), "offline-processing-output.yml");
// Configure a logger to output to the console.
var loggerFactory = LoggerFactory.Create(b => b.AddConsole());
var logger = loggerFactory.CreateLogger<Program>();
if (dataFile != null)
{
using (var writer = new StreamWriter(File.OpenWrite(outputFile)))
using (var reader = new StreamReader(File.OpenRead(evidenceFile)))
{
new Example().Run(dataFile, reader, loggerFactory, writer);
}
logger.LogInformation($"Processing complete. See results in: '{outputFile}'");
}
else
{
logger.LogError("Failed to find a device detection data file. Make sure the " +
"device-detection-data submodule has been updated by running " +
"`git submodule update --recursive`.");
}
// Dispose the logger to ensure any messages get flushed
loggerFactory.Dispose();
}
}
}