①定义一个要被监视的对象

1 class TestClass 2     { 3         private string value; 4         public string Value 5         { 6             get { return value; } 7  8             set 9             {10                 this.value = value;11                 Notify();12             }13         }14 15         public event EventHandler
      
        ValueChanged;16 17         private void Notify()18         {19             if (ValueChanged != null)20             {21                 ValueChanged(this, this);22             }23         }24 25     }
      

②观察者订阅该事件

 Program.testClass.ValueChanged += testClass_ValueChanged; 

③在事件处理程序中处理相关逻辑

 this.textBox1.Text = Program.testClass.Value;