Получить сумму значения столбца ObservableCollection

Question

Как получить сумму значения столбца ObservableCollection к другому свойству при изменении значений столбцов данных в сети, - МОФ MVVM патерн

Answer 1

Вот решение:

Xaml:

<Window x:Class="Mvvm.MainWindow" 
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
     xmlns:System="clr-namespace:System;assembly=mscorlib" 
     Title="MainWindow" Height="300" Width="400" > 
    <Grid> 
     <Grid.RowDefinitions> 
      <RowDefinition Height="*"/> 
      <RowDefinition Height="20"/> 
     </Grid.RowDefinitions> 
     <DataGrid Grid.Row="0" 
        ItemsSource="{Binding VM.MyList}" 
        SelectedItem="{Binding VM.MyItem , Mode=TwoWay}" 
        /> 
     <TextBlock Grid.Row="1" Text="{Binding VM.Sum}"/> 
    </Grid> 
</Window> 

Просмотр моделей:

public class MainViewModel : INotifyPropertyChanged 
{ 
    #region INotifyPropertyChanged 
    public event PropertyChangedEventHandler PropertyChanged; 
    void OnPropertyChanged(string propertyName) 
    { 
     if (PropertyChanged != null) 
      PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); 
    } 
    #endregion 

    public ObservableCollection<ItemViewModel> MyList { get; set; } 

    ItemViewModel _myItem; 
    public ItemViewModel MyItem 
    { 
     get 
     { 
      return _myItem; 
     } 
     set 
     { 
      _myItem = value; 
      OnPropertyChanged("MyItem"); 
      OnPropertyChanged("Sum"); 
     } 
    } 

    public int Sum 
    { 
     get 
     { 
      return MyList.Sum(a=>a.Amount); 
     } 
    } 

    public MainViewModel() 
    { 
     MyList = new ObservableCollection<ItemViewModel>(); 

     MyList.Add(new ItemViewModel { Amount = 5}); 
     MyList.Add(new ItemViewModel { Amount = 6}); 
    } 

} 

public class ItemViewModel : INotifyPropertyChanged 
    { 
     #region INotifyPropertyChanged 
     public event PropertyChangedEventHandler PropertyChanged; 
     void OnPropertyChanged(string propertyName) 
     { 
      if (PropertyChanged != null) 
       PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); 
     } 
     #endregion 

     int _amount; 
     public int Amount 
     { 
      get 
      { 
       return _amount; 
      } 
      set 
      { 
       _amount = value; 
       OnPropertyChanged("Amount"); 
      } 
     } 
     //Other properties like Id, transactionDate, ... 

    } 

Главный код окна позади:

public MainViewModel VM { get; set; } 
    public MainWindow() 
    { 
     InitializeComponent(); 
     VM = new MainViewModel(); 
     DataContext = this; 

    }