public class MyEntity : Microsoft.WindowsAzure.Storage.Table.TableEntity
{
    public TimeSpan MyDuration { get; set; }

    // Workaround the fact that TableEntity does not automatically store a `TimeSpan`
    public long MyDurationTicks
    {
        get { return MyDuration.Ticks; }
        set { MyDuration = TimeSpan.FromTicks(value); }
    }
}