Calculate the exponential moving average of a stream of numbers

public static IEnumerable<double> ExponentialMovingAverage(this IEnumerable<double> source, double alpha)
{
    double? last = null;
    return source.Select(
        value =>
        {
            var average = last != null ? alpha*value + (1 - alpha)*last.Value : value;
            last = average;
            return average;
        });
}

Create a fast compiled method invoker using LINQ

var method = new Func<double, double, double>(Math.Pow).Method;
var parameter = Expression.Parameter(typeof(object[]));
var args = method.GetParameters()
    .Select((param, i) => Expression.Convert(
        Expression.ArrayIndex(parameter, Expression.Constant(i)), param.ParameterType));
var expr = Expression.Lambda<Func<object[], object>>(
    Expression.Convert(Expression.Call(method, args), typeof(object)), parameter);
var invoker = expr.Compile();
var result = invoker(new object[] {Math.PI, 2.0});

Create a Google calendar event in an existing calendar

var credentials = new GDataCredentials(userName, password);
var service = new CalendarService(null) {Credentials = credentials};
var query = new CalendarQuery("https://www.google.com/calendar/feeds/default/owncalendars/full");
var feed = service.Query(query);
var eventFeedLink = feed.Entries.Cast<CalendarEntry>()
    .Where(item => item.Title.Text == calendarName)
    .SelectMany(item => item.Links)
    .First(link => link.Rel == GDataParserNameTable.NSGCal + "#eventFeed");
var entry = new EventEntry(title) {Times = {new When(start, end, allDay)}};
service.Insert(new Uri(eventFeedLink.AbsoluteUri), entry);

Google Data API .NET client library

Page through potentially large NHibernate criteria query results

public static IEnumerable<T> Enumerate<T>(this ICriteria criteria, int pageSize = 1000)
{
    var entityCount = CriteriaTransformer.TransformToRowCount(criteria).UniqueResult<int>();
    var pageCount = (int) Math.Ceiling(entityCount/(double) pageSize);
    criteria = CriteriaTransformer.Clone(criteria).SetMaxResults(pageSize);
    return Enumerable.Range(0, pageCount)
        .SelectMany(pageNum => criteria.SetFirstResult(pageNum*pageSize).List<T>());
}

NHibernate

Create a YouTube playlist containing all the uploads of a given user

var credentials = new GDataCredentials(userName, password);
var service = new YouTubeService(applicationName, developerKey) {Credentials = credentials};
var entry = new AtomEntry {Title = {Text = playlistName}};
entry = service.Insert(new Uri(YouTubeQuery.CreatePlaylistsUri(null)), entry);
var id = ((XmlExtension) entry.FindExtension("playlistId", YouTubeNameTable.NSYouTube)).Node.InnerText;
var batchUri = new Uri(string.Format("https://gdata.youtube.com/feeds/api/playlists/{0}/batch", id));
var query = new YouTubeQuery(YouTubeQuery.CreateUserUri(sourceUser)) {StartIndex = 1};
AtomFeed feed;
do
{
    feed = service.Query(query);
    service.Batch(feed, batchUri);
    query.StartIndex += feed.Entries.Count;
} while (query.StartIndex < feed.TotalResults);

Google Data API .NET client library

List the users of a TFS project associated with a local workspace path

var workspace = Workstation.Current.GetLocalWorkspaceInfo(path);
var tfs = new TfsTeamProjectCollection(workspace.ServerUri);
var gss = tfs.GetService<IGroupSecurityService>();
var grp = gss.ReadIdentity(SearchFactor.EveryoneApplicationGroup, null, QueryMembership.Expanded);
var names = gss.ReadIdentities(SearchFactor.Sid, grp.Members, QueryMembership.None)
    .Where(identity => identity.Type == IdentityType.WindowsUser)
    .Select(identity => string.Format(@"{0}\{1}", identity.Domain, identity.AccountName))
    .ToArray();

Quartz scheduler job that re-triggers itself on completion

public class RetriggerJob : IInterruptableJob
{
    private bool _interrupted;
    public void Execute(IJobExecutionContext context)
    {
        Thread.Sleep(1000);
        if (_interrupted)
        {
            return;
        }
        context.Scheduler.TriggerJob(context.JobDetail.Key);
        if (_interrupted)
        {
            context.Scheduler.Interrupt(context.JobDetail.Key);
        }
    }
    public void Interrupt()
    {
        _interrupted = true;
    }
}

Quartz.NET