怎样实现关闭一个动态创建的窗体,求大虾帮助下

using System;
using System.Collections.Generic;
using
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
namespace myform
{    public class From1:Form
    {      public Form1()
        {
            InitializeComponent();//主窗体直接 拖用的控件
        }
    private void button3_Click(object sender, EventArgs e)//点击这个按钮就会弹出一个新的窗口
    {    Form SubForm=new Form();
         subForm.show();       //subForm上有一btn_OK按钮
    }
     private void btn_OK_Click(object sender, EventArgs e)//怎么实现按下btn_OK按钮关闭SubForm
        {                                                               
        }
}