public class ViewModel : INotifyPropertyChanged
        {
            private ObservableCollection<TimeModel> _testData;
            public ObservableCollection<TimeModel> TestData
            {
                get { return _testData; }
                set
                {
                    _testData = value;
                    OnPropertyChanged("TestData");
                }
            }
            public ViewModel()
            {
                TestData = new ObservableCollection<TimeModel>();
                TestData.Add(new TimeModel() { Time1 = new DateTime(2022,10,31,1,0,0 ), Time2 = new DateTime(2022, 10, 31, 1, 0, 0) });
                TestData.Add(new TimeModel() { Time1 = new DateTime(2022, 10, 31, 2, 0, 0), Time2 = new DateTime(2022, 10, 31, 2, 0, 0) });
            }
            public event PropertyChangedEventHandler PropertyChanged;
            private void OnPropertyChanged(String propertyName)
            {
                PropertyChangedEventHandler handler = PropertyChanged;
                if (handler != null)
                {
                    handler(this, new PropertyChangedEventArgs(propertyName));
                }
            }
        }
        public class TimeModel : INotifyPropertyChanged
        {
            private DateTime time1;
            public DateTime Time1
            {
                get { return time1; }
                set
                {
                    time1 = value;
                    OnPropertyChanged("Time1");
                    OnPropertyChanged("Time3");
                }
            }
            private DateTime time2;
            public DateTime Time2
            {
                get { return time2; }
                set
                {
                    time2 = value;
                    OnPropertyChanged("Time2");
                    OnPropertyChanged("Time3");
                }
            }
            public DateTime Time3
            {
                get
                {
                   
                    var date = new DateTime(Time1.Year , Time1.Month , Time1.Day , Time1.Hour + Time2.Hour, Time1.Minute + Time2.Minute, Time1.Second + Time2.Second);
                    return date;
                } 
            }
            public event PropertyChangedEventHandler PropertyChanged;
            private void OnPropertyChanged(String propertyName)
            {
                PropertyChangedEventHandler handler = PropertyChanged;
                if (handler != null)
                {
                    handler(this, new PropertyChangedEventArgs(propertyName));
                }
            }
        }