public async Task ClearRegistration(Event @event)
{
bool ok = await CustomPersistence.Delete(@event.Id, _uri + "ClearEvent/");
if (ok)
{
Registrations.RemoveAll(x => x.EventId == @event.Id);
RegistrationDictionary[@event].Clear();
}
else
{
throw new BaseException("Clear regi fail");
}
}