Example usage of the Microsoft.Azure.CognitiveServices.Vision.Face Nuget package

facial-recognition-sample.cs

public async Task Recognize(Stream imageStream)
{
  var faceClient = new FaceClient(new ApiKeyServiceClientCredentials(FaceSubscriptionKey))
  {
    Endpoint = "https://westus.api.cognitive.microsoft.com"
  };

  try
  {
    Console.WriteLine(DateTime.Now + ": Attempting to recognize faces...");

    var detectedFaces = await faceClient.Face.DetectWithStreamAsync(imageStream, true, true);
    var faceIds = detectedFaces.Where(f => f.FaceId.HasValue).Select(f => f.FaceId.Value).ToList();

    if (faceIds.Any())
    {
      var potentialUsers = await faceClient.Face.IdentifyAsync(faceIds, FaceGroupId);
      foreach (var candidate in potentialUsers.Select(u => u.Candidates.FirstOrDefault()))
      {
        var candidateName = await GetCandidateName(candidate?.PersonId);
        Console.WriteLine("{0}: {1} ({2})", DateTime.Now, candidateName, candidate?.PersonId);
      }
    }
  }
  catch (APIErrorException apiError)
  {
    Console.WriteLine("Cognitive service error: " + apiError?.Body?.Error?.Message);
  }
  catch (Exception e)
  {
    Console.WriteLine("Getting identity failed: " + e.ToString());
  }
}


private static IList<Person> _cachedIdentities = null;
private async static Task<string> GetCandidateName(FaceClient faceClient, Guid? personId)
{
  if (!personId.HasValue)
  {
    return "No Person ID";
  }

  if (_cachedIdentities == null)
  {
    _cachedIdentities = await faceClient.PersonGroupPerson.ListAsync(FaceGroupId);
  }

  return _cachedIdentities
    ?.Where(i => i.PersonId == personId)
    .Select(i => i.Name)
    .FirstOrDefault()
    ?? "Candidate not found";
}