静态对象解除及关联事件的问题

Question

public class Employee : System.ComponentModel.INotifyPropertyChanged
{
private string _name;
public string Name
{
get{return _name;}
set{if(_name != value){
_name =value;
SendPropertyChanged("Name:"+value);
}}
}
public event System.ComponentModel.PropertyChangedEventHandler PropertyChanged;
protected virtual void SendPropertyChanged(String propertyName)
{
if ((this.PropertyChanged != null))
{
this.PropertyChanged(this, new System.ComponentModel.PropertyChangedEventArgs(propertyName));
}
}
}public class ClassTest
{
public ClassTest()
{    
   Gloal.Em.PropertyChanged -= Employee_PropertyChanged;
   Gloal.Em.PropertyChanged += Employee_PropertyChanged;
}
private void Employee_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
{
Console.WriteLine(e.PropertyName);
}
}public class Gloal
{
   public static Employee Em;
}static class Program
{
   [STAThread]
   static void Main(string[] args)
   {
Gloal.Em = new Employee{Name = "a"}; ClassTest t = new ClassTest();
Gloal.Em.Name = "b";

ClassTest t1 = new ClassTest();
Gloal.Em.Name = "c";

ClassTest t2 = new ClassTest();
ClassTest t12 = new ClassTest();
Gloal.Em.Name = "d";
   }
｝
输出结果：
Name:b
Name:c
Name:c
Name:d
Name:d
Name:d
Name:d-= 为啥不起作用呢?

Answer 1

       Gloal.Em.PropertyChanged -= Employee_PropertyChanged;    
       Gloal.Em.PropertyChanged += Employee_PropertyChanged;
你减完了，又加上了

Answer 2

SendPropertyChanged("Name:"+value);
改为：
SendPropertyChanged("Name:");
试试~~

Answer 3

减完了，又加上了，就是想确保只关联一次。Gloal.Em.Name = "d"的时候，触发了4次!

Answer 4

public ClassTest()
    {       
       Gloal.Em.PropertyChanged -= Employee_PropertyChanged;    
       Gloal.Em.PropertyChanged += Employee_PropertyChanged;
    }
    private void Employee_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
    {
        Console.WriteLine(e.PropertyName);
    }=》 public ClassTest()
        {
            
            Gloal.Em.PropertyChanged += Employee_PropertyChanged;
        }
        private void Employee_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
        {
            Console.WriteLine(e.PropertyName);
            Gloal.Em.PropertyChanged -= Employee_PropertyChanged;
        }说实话这样子在一个实例构造函数里面去改变一个静态变量 我觉得出问题很正常~