将自定义属性绑定到Entity Framework

Question

I am building a C# application using the Entity framework.

I have an Entity which was created from my database which has fields "Price" and "Quantity".

Using a partial class declaration I created a custom property "SubTotal" as follows:

partial class Detail {
  public decimal Subtotal {
    get
    {
      return Price * Quantity;
    }
  }  
}

The thing is, I use a lot of DataBinding in my application.

Somewhere, I use an IBindingList<Detail> as ItemsSource for a ListView.

When I modify (using code-behind) some elements of the list, the quantity and price, the listview is updated properly.

However, the Subtotal is not updated.

I think that it's because something is done automatically by the entity framework to notify that something has been changed, but I don't know what to add to my custom property so that it behaves the same way.

Could you help me out?

Answer 1

对我有用的是调用OnPropertyChanged方法：

OnPropertyChanged("CustomPropertyName")

Answer 2

The UI doesn't know that the value of Subtotal is changed. Implement System.ComponentModel.INotifyPropertyChanged , and then raise the PropertyChanged event to let the UI know that Subtotal has changed when either Price or Quantity has changed.

For example:

partial class Detail : INotifyPropertyChanged {

   public decimal Subtotal 
   {
      get
      {
         return Price * Quantity;
      }
   }  

   public event PropertyChangedEventHandler PropertyChanged;

   private void NotifyPropertyChanged(String info)
   {
      if (PropertyChanged != null)
      {
          PropertyChanged(this, new PropertyChangedEventArgs(info));
      }
   }
}

Then when Price or Quantity is changed, you'd call NotifyPropertyChanged("Subtotal") , and the UI should update the displayed value of Subtotal appropriately.