gistfile1.cs

using Examine.LuceneEngine.SearchCriteria;

var Searcher = Examine.ExamineManager.Instance.SearchProviderCollection["InternalMemberSearcher"];
var searchCriteria = Searcher.CreateSearchCriteria(Examine.SearchCriteria.BooleanOperation.Or);
var query = searchCriteria.RawQuery("githubUsername:"+payload.PullRequest.User.Login);
var searchResults = Searcher.Search(query);

var memberId = searchResults.First().Id;