protected override void OnInitialize()
        {
            base.OnInitialize();

            Rejects = Begin.Concat(End)
                      .Do(_ => IsLoading.Value = true)
                      .Select(_ => RxQuery(s => {
                var begin  = Begin.Value;
                var end    = End.Value.AddDays(1);
                var result = s.Query <Reject>()
                             .Where(r => r.LetterDate >= begin && r.LetterDate < end)
                             .OrderBy(r => r.LetterDate)
                             .ToList();
                return(result);
            }))
                      .Switch()
                      .Do(_ => IsLoading.Value = false)
                      .ToValue(CloseCancellation);
        }