protected void Page_Load(object sender, EventArgs e)
    {
                   for (int i = 0; i < GridView1.Rows.Count; i++)
            {
                LinkButton LinkButton3 = (LinkButton)this.GridView1.Rows[i].Cells[4].FindControl("LinkButton3");
                if (CheckBox1.Checked)
                {
                    LinkButton3.CssClass = "show";//找不到控件，未将对象引用设置的对象的实例
                }
                else
                {
                    LinkButton3.CssClass = "hidden";
                }
            }   
    }