#region 清除
    protected void btnClear_Click(object sender, EventArgs e)
    {
        foreach (Control ctl in this.Controls)
        {
            this.txtClear(ctl);
        }
    }
    #endregion

    private void txtClear(Control ctls)
    {
        if(ctls.HasControls())
        {
            foreach (Control ctl in ctls.Controls)
            {
                txtClear(ctl);
            }
        }
        else
        {
            if (ctls.GetType().Name == "TextBox")
            {
                TextBox tb = new TextBox();
                tb = (TextBox)this.FindControl(ctls.ID);
                tb.Text = "";
            }
            else if (ctls.GetType().Name == "DropDownList")
            {
                DropDownList ddl = new DropDownList();
                ddl = (DropDownList)this.FindControl(ctls.ID);
                ddl.SelectedIndex = 1;
            }
        }
    }