c#下载存在数据库的文件代码

public partial class dwon : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        int fileID =int.Parse( Request.QueryString["id"].ToString());
         SqlConnection con = new SqlConnection(SqlHelper.connstring);
        con.Open();
        string sql = "select * from Files where id='" + fileID + "'";
        SqlCommand cmd = new SqlCommand(sql, con);
        SqlDataReader sdr = cmd.ExecuteReader();
        sdr.Read();
        Response.Buffer = true;
        Page.Response.Clear();//清除缓冲区所有内容
        Page.Response.ContentType = sdr["fileType"].ToString();
        Page.Response.AddHeader("Content-Disposition", "attachment;FileName=" + HttpUtility.UrlEncode(sdr["FileName"].ToString() +"."+ HttpUtility.UrlEncode(sdr["fileType"].ToString())));
        byte[] file = (Byte[])sdr["fileData"];//读出数据
         
       
        int a = file.Length;
        Response.BinaryWrite(file);
        Response.Flush();
        Response.End();
        sdr.Close();
        con.Close();
    }
}