C＃每次更改其他值使用mvvm

Question

我有一个DataGrid绑定到一个ObservableCollection<Item>。当我更改物料的数量时，我想自动更改物料的总量。这是Quantity*Cost=Total

<DataGrid ItemsSource="{Binding Invoices.Items}" AutoGenerateColumns="False"> 
    <DataGridTextColumn Header="Name" Binding="{Binding Name}" /> 
    <DataGridTextColumn Header="Quantity" Binding="{Binding Quantity}" /> 
    <DataGridTextColumn Header="Cost" Binding="{Binding Cost}" /> 
    <DataGridTextColumn Header="Total" Binding="{Binding Total}" /> 
</DataGrid> 

视图模型是改变简单的”

public class ViewModel:BaseClass 
{ 
    public ViewModel() 
    { 
     FillInvoice(); 
    } 

    private Invoice _invoice; 
    public Invoice Invoice 
    { 
     get { return _invoice; } 
     set 
     { 
      if (_invoice!=value) 
      { 
       _invoices = value; 
       OnPropertyChanged(); 
      } 
     } 
    } 

    private void FillInvoice() 
    { 
     var customer = new Customer() {Id=1,Name = "James"}; 
     var invoice = new Invoice() {Customer = customer, Id = 1,CustomerId = 1}; 
     var item = new Item() {Cost = Convert.ToDecimal(12.50),Id = 1,Name = "Item"}; 
     for (int i = 0; i < 10; i++) 
     { 
      invoice.Items.Add(item); 
     } 
     Invoices = invoice; 
    } 
} 

发票是这样的：

public Invoices() 
{ 
    Items=new ObservableCollection<Item>(); 
} 
public int Id { get; set; } 
public int CustomerId { get; set; } 
public Customer Customer { get; set; } 
public ObservableCollection<Item> Items { get; set; } 

我的项目是这样的：

public class Item:BaseClass 
{ 
    private string _name; 
    private decimal _cost; 
    public int Id { get; set; } 
    public string Name 
    { 
     get { return _name; } 
     set 
     { 
      if (_name!=value) 
      { 
       _name = value; 
       OnPropertyChanged(); 
      } 
     } 
    } 

    private int _quantity; 
    public int Quantity 
    { 
     get { return _quantity; } 
     set 
     { 
      if (_quantity!=value) 
      { 
       _quantity = value; 
       OnPropertyChanged(); 
      } 
     } 
    } 

    public decimal Cost 
    { 
     get { return _cost; } 
     set 
     { 
      if (_cost!=value) 
      { 
       _cost = value; 
       OnPropertyChanged(); 
      } 
     } 
    } 

    private decimal _total; 

    public decimal Total 
    { 
     get { return _total; } 
     set 
     { 
      if (_total != value) 
      { 
       _total = value; 
       OnPropertyChanged(); 
      } 

     } 
    } 

} 

我是什么思考是广告将一个事件处理程序添加到数量项目中，它将计算总计，但我不确定如何执行添加。

public ViewModel(){ 
    Invoice.Items.Quantity.PropertyChanged += (s,e) 
    { 
     Total = Cost*Quantity 
    } 
} 



public Item() 
{ 
    Quantity.PropertyChanged += (s,e) 
    { 
     Total = Cost*Quantity 
    } 
} 

但它不能编译它们。

Answer 1

你可以只实现总的计算性能，如果总是等于成本*数量，因为在存储冗余数据方面没有意义：

public decimal Total 
{ 
    get { return Cost * Quantity; } 
} 

这应该就可以了，假设没有参数的OnPropertyChanged（）会触发一个泛型/空属性更改事件，这将导致所有订阅的属性被重新检查。

Answer 2

尝试增加OnPropertyChanged("Total");您Quantity属性：

private int _quantity; 
public int Quantity 
{ 
    get { return _quantity; } 
    set 
    { 
     if (_quantity!=value) 
     { 
      _quantity = value; 
      OnPropertyChanged(); 
      Total = Cost*Quantity 
      OnPropertyChanged("Total"); 
     } 
    } 
} 

Answer 3

你可以写你的属性中的代码如下所示：

private decimal _total; 
private int _quantity; 
private decimal _cost 

public decimal Quantity 
{ 
    get { return _quantity; } 
    set 
    { 
     _quantity = value; 
     Total = _quantity * _cost; 
    } 
} 

public decimal Total 
{ 
    get { return _total; } 
    set 
    { 
     if (_total != value) 
     { 
      _total = value; 
      OnPropertyChanged(); 
     } 
    } 
}