我弄清楚了自己.

第一步:
在父WindowsForm中创建一个方法.它应该是虚拟的.然后，在子WindowsForm中无法处理的控件的处理程序方法中，我将方法称为"Do".

I figure out myself.

First step:
Create a method in parent WindowsForm. it should be virtual. Then in the handler method of a control which I couldn''t handle it in child WindowsForm, I call method "Do".

public System.Drawing.Forms.Form CRUD
{
  public virtual void Do()
  {
     //
  } 
  public void Control_Click(object sender, EventArg e)
  {
     Do();
  }
}

第二步:
现在，通过覆盖方法"Do"，我可以做我想做的事情.

Second step:
Now by overriding method "Do", I can do what I want.

public System.Drawing.Forms.Form CountryUI: CRUD
{
  public override void Do()
  {
    //some code..
  }
}

我忽略了一个事件.是吗?

I overrided an event. did I?