// 假如按下“Add”按钮，那么count加一
        string target = this.Request["btnAdd"];
        if (target == "Add")
        {
            _count++;
        }

        // 动态创建控件
        for (int i = 0; i < _count; i++)
        {   // 这里以TextBox为例，实际上需要创建的是WebPartZone
            TextBox newTextbox = new TextBox();
            newTextbox.ID = "TXT" + i.ToString();
            this.PlaceHolder1.Controls.Add(newTextbox);
        }
    }

    protected void Page_Load(object sender, EventArgs e)
    {
        hfCount.Value = _count.ToString();
    }

    protected void btnAdd_Click(object sender, EventArgs e)
    {
        // 不能在此添加WebPartZone控件，只能在OnInit或之前，否则报异常
    }
}
希望大家能提出更好的解决方案，我拭目以待，呵呵@_@
http://www.cnblogs.com/leafyoung/archive/2007/04/04/699465.html