Executing

ResultSet<IEvent> rs = query.Execute();
ResultSet<IEvent> rs = await query.ExecuteAsync();

IEvent? one   = query.FirstOrDefault();      // also FirstOrDefaultAsync()
IEvent  first = query.First();               // also FirstAsync()
IEvent  only  = query.Single();              // throws unless exactly one matches

if (query.TryGet(out var ev)) { … }          // false for none, throws for more than one