WPF INotifyPropertyChanged

public class OrderModel:INotifyPropertyChanged
{
  public string _oderID;
  public string OrderID;
    {
        get
        {
           return _orderID;
        }
        set
        {
          if(_oderID==value)
               return;
          _orderID=value;
          NotifyPropertyChanged("OrderID");
        }  
     }
	
   public event PropertyChangedEventHandler PropertyChanged;
   private void NotifyPropertyChanged(string propertyname)
   {
	if(PropertyChanged!=null)
	{
		PropertyChanged(this,new PropertyChangedEventArgs(propertyname));
	}
    }        
}    

　　集合或者属性的改变是需要通知ＵＩ，ＵＩ才会发生变化的

１.集合的通知接口：INotifyCollectionChanged

2.属性的通知接口:INotifyPropertyChanged

ObervableCollection实现了INotifyCollectionChanged接口，List没有实现