aspx导出到excel 无中文乱码问题

protected void LinkButton1_Click(object sender, EventArgs e)
{

        Response.ClearContent();        Response.Clear();        Response.AddHeader("content-disposition", "attachment; filename=sumlate.xls");        Response.Charset = "GB2312";        Response.ContentEncoding = System.Text.Encoding.GetEncoding("GB2312");        Response.ContentType = "application/excel";        System.IO.StringWriter sw = new System.IO.StringWriter();        HtmlTextWriter htw = new HtmlTextWriter(sw);        if (GridView1.Rows.Count > 0)        {            GridView1.RenderControl(htw);        }        else        {            GridView1.RenderControl(htw);        }        Response.Write(sw.ToString());        Response.End();    }    public override void VerifyRenderingInServerForm(Control control)    {        //这个方法不能删除掉    }