Question

我正在使用 MVVM Light Toolkit 开发 WPF 应用程序。我只想显示一个嵌套的Observablecollection，它将Employee Attendance详细信息保存到DataGrid并在内部网格中执行一些CRUD功能，并根据这些更改自动重新计算外部收集记录。内部集合（PunchDetailModels）显示在RowDetailsTemplate的{{1}}中。

以下是模特：

DataGrid

ViewModel：

    public class AttendanceModel : ObservableObject
     {
        public const string EmpNamePropertyName = "EmpName";

        private string _empName = string.Empty;

        public string EmpName
        {
            get
            {
                return _empName;
            }
            set
            {
                Set(EmpNamePropertyName, ref _empName, value);
            }
        }

        public const string PunchDetailModelsPropertyName = "PunchDetailModels";

        private ObservableCollection<PunchDetailModel> _punchDetailModels = null;

        public ObservableCollection<PunchDetailModel> PunchDetailModels
        {
            get
            {
                return _punchDetailModels;
            }
            set
            {
                Set(PunchDetailModelsPropertyName, ref _punchDetailModels, value);
            }
        }           
        private string _inOutCount;
        public string InOutCount
        {
                get
                {
                    return PunchDetailModels != null
                        ? string.Format("{0}/{1}", PunchDetailModels.Count(i => i.PunchStatus == Enums.PunchType.CheckIn),
                            PunchDetailModels.Count(i => i.PunchStatus == Enums.PunchType.CheckOut))
                        : null;
                }
            }

        public TimeSpan? FirstCheckIn
        {
            get
            {
                if (_punchDetailModels != null)
                {
                    var firstCheckIn =
                        _punchDetailModels.OrderBy(t => t.PunchTime)
                            .FirstOrDefault(i => i.PunchStatus == Enums.PunchType.CheckIn);

                    if (firstCheckIn != null)
                        return firstCheckIn.PunchTime;
                }

                return null;
            }
        }


        public TimeSpan? LastCheckOut
        {
            get
            {
                if (_punchDetailModels != null)
                {
                    var lastCheckOut =
                        _punchDetailModels.OrderBy(t => t.PunchTime)
                            .LastOrDefault(o => o.PunchStatus == Enums.PunchType.CheckOut);
                    if (lastCheckOut != null)
                        return lastCheckOut.PunchTime;
                }

                return null;
            }
        }


        public TimeSpan? TotalInTime
        {
            get
            {
                TimeSpan totalInTime = TimeSpan.Zero;

                if (_punchDetailModels != null)
                {
                    if (!IsValidRecord()) return null;

                    for (int inTime = 0; inTime < _punchDetailModels.Count; inTime += 2)
                    {
                        totalInTime += _punchDetailModels[inTime + 1].PunchTime - _punchDetailModels[inTime].PunchTime;
                    }
                }

                return totalInTime;
            }
        }

        public TimeSpan? TotalOutTime
        {
            get
            {
                TimeSpan totalInTime = TimeSpan.Zero;

                if (_punchDetailModels != null)
                {
                    if (!IsValidRecord()) return null;

                    for (int inTime = 1; inTime < _punchDetailModels.Count - 1; inTime += 2)
                    {
                        totalInTime += _punchDetailModels[inTime + 1].PunchTime - _punchDetailModels[inTime].PunchTime;
                    }
                }

                return totalInTime;
            }
        }    
}

public class PunchDetailModel : ObservableObject
    {
        public const string PunchStatusPropertyName = "PunchStatus";

        private Enums.PunchType _punchStatus;

        public Enums.PunchType PunchStatus
        {
            get
            {
                return _punchStatus;
            }
            set
            {
                Set(PunchStatusPropertyName, ref _punchStatus, value);
            }
        }

        public const string PunchTimePropertyName = "PunchTime";

        private TimeSpan _punchTime = TimeSpan.Zero;

        public TimeSpan PunchTime
        {
            get
            {
                return _punchTime;
            }
            set
            {
                Set(PunchTimePropertyName, ref _punchTime, value);
            }
        }

    }

查看： enter image description here

我面临的问题：

1）当用户 ADD 或删除来自Inner DataGrid的特定记录时，我需要在视图模型中获取通知。我知道通过为ObservableCollection注册一个集合更改事件是可能的。但内部public const string AttendanceCollectionPropertyName = "AttendanceCollection"; private ObservableCollection<AttendanceModel> _attendanceCollection = null; public ObservableCollection<AttendanceModel> AttendanceCollection { get { if (_attendanceCollection == null) { _attendanceCollection = new ObservableCollection<AttendanceModel>(); //_attendanceCollection.CollectionChanged+=_attendanceCollection_CollectionChanged; } return _attendanceCollection; } set { Set(AttendanceCollectionPropertyName, ref _attendanceCollection, value); } }怎么可能？

2）我需要在viewmodel中获取Inner DataGrid中CheckIn或Checkout字段的任何更改通知，以便我可以重新计算TotalInTime，TotalOutTime等字段。

我该怎么做？我目前仍然坚持这种情况。请提出您的宝贵意见。

Answer 1

我猜测ObservableObject类是您自己的INotifyPropertyChanged接口实现。现在来解决你的问题：

您应该在CollectionChanged中注册_punchDetailModels事件并在处理程序中为该变量举起PropertyChanged事件，如下所示：

 public ObservableCollection<PunchDetailModel> PunchDetailModels
{
  get
  {
    return _punchDetailModels;
  }
  set
  {
    Set(PunchDetailModelsPropertyName, ref _punchDetailModels, value);
     _punchDetailModels.CollectionChanged += handler;
  }
 }           
  private void handler(object sender, NotifyCollectionChangedEventArgs e)
  {
    base.RaisePropertyChanged(PunchDetailModelsPropertyName); // If you don't have a method with such signature in ObservableObject (one that takes a string and raises PropertyChanged for it) you'll have to write it.
   }

这样，在从内部集合添加或删除元素时，视图应自动重新加载。

没有其他方式可以订阅在这些字段上收听PropertyChanged。这就是View所做的事情，这也是ViewModel应该做的事情。像这样：

 public const string AttendanceCollectionPropertyName = "AttendanceCollection";

 private ObservableCollection<AttendanceModel> _attendanceCollection = null;
 public ObservableCollection<AttendanceModel> AttendanceCollection
  {
   get
   {
    if (_attendanceCollection == null)
    {
        _attendanceCollection = new ObservableCollection<AttendanceModel>();
    }
    return _attendanceCollection;
  }
   set
  {
    Set(AttendanceCollectionPropertyName, ref _attendanceCollection, value);
    _attendanceCollection.CollectionChanged+= handler
  }
} 

 private void handler(object sender, NotifyCollectionChangedEventArgs e)
 {
  foreach (AttendanceModel model in AttendanceCollection)
        model.PropertyChanged += somethingChanged;
  }

  // Very ineffective to subscribe to all elements every time a list changes but I leave optimization to you.
 private somethingChanged (object obj, PropertyChangedEventArgs args)
 {
   if ( args.PropertyName == "CheckIn" ) // for example
    { 
          AttendanceModel ModelToRecalculate = obj as AttendanceModel;
          // You can do anything you want on that model.
    }
 }

当然，当您认为有必要时，您需要在PropertyChanged课程中使用string CheckIn参数值AttendanceModel来提升handler（例如{{1}方法）

修改

回答你的评论问题：

“来到第二个 - 我需要重新计算出勤模型属性，如InOutCount，TotalInTime，PunchTime字段更新中的TotalOutTime。”

答案是：您无需在ViewModel中执行任何操作即可“重新计算”。用户界面订阅PropertyChange InOutCount，FirstCheckIn ...等等。这是Binding（它自动完成）。

所以，您需要做的就是通知UI需要重新计算给定模型的是调用RaisePropertyChanged("InOutCount")，RaisePropertyChanged("FirstCheckIn")。用户界面将理解它需要获取这些属性，并且因为你在属性获取器中有这些计算，它将被重新计算。

因此，我发现每次INNER列表更改时都需要重新计算UI，因此您需要做的就是将handler代码更改为CollectionChanged PunchDetailModels ：

// the handler for CollectionChanged for the INNER collection (PunchDetailModels) private void handler(object sender, NotifyCollectionChangedEventArgs e) { base.RaisePropertyChanged(PunchDetailModelsPropertyName); // If you don't have a method with such signature in ObservableObject (one that takes a string and raises PropertyChanged for it) you'll have to write it. base.RaisePropertyChanged("InOutCount") base.RaisePropertyChanged("FirstCheckIn") base.RaisePropertyChanged("LastCheckOut") // and so on for all the properties that need to be refreshed }

嵌套的ObservableCollection - 从子到父的Propogate通知

1 个答案: