Encryption mvc5中的文件加密

在mvc5中的grid view下载文件后，我立即加密该文件，但我得到的是0字节的加密文件，当我重新下载该文件时，我得到的是正确的加密文件。有人能告诉我代码有什么问题吗？或者下载后我必须延迟加密功能一段时间使用吗系统安全

var graphids = from o in db.OfflineCarts
                               join i in db.Graphs on o.ItemId equals i.ItemUserID
                               select i;

            GridView gv = new GridView();
            gv.DataSource = graphids.ToList();
            gv.DataBind();
            Response.ClearContent();
            Response.Buffer = true;
            Response.AddHeader("content-disposition", "attachment; filename=GraphTable.xls");
            Response.ContentType = "application/ms-excel";
            Response.Charset = "";
            StringWriter sw = new StringWriter();
            HtmlTextWriter htw = new HtmlTextWriter(sw);
            gv.RenderControl(htw);
            Response.Output.Write(sw.ToString());
            Response.Flush();
            Response.End();
            Encryption();


    public void Encryption()
    {

        string password = @"myKey123"; // Your Key Here
        UnicodeEncoding UE = new UnicodeEncoding();
        byte[] key = UE.GetBytes(password);

        string cryptFile = "/Users/Neeraj/Downloads/UserFilesEncrypt.xls";
        FileStream fsCrypt = new FileStream(cryptFile, FileMode.CreateNew);

       RijndaelManaged RMCrypto = new RijndaelManaged();
       CryptoStream rs = new CryptoStream(fsCrypt,
          RMCrypto.CreateEncryptor(key, key),
          CryptoStreamMode.Read);

        CryptoStream cs = new CryptoStream(fsCrypt,
            RMCrypto.CreateEncryptor(key, key),
            CryptoStreamMode.Write);

        string inputFile = "/Users/Neeraj/Downloads/GraphTable.xls";
        FileStream fsIn = new FileStream(inputFile, FileMode.Open);

        int data;
        while ((data = fsIn.ReadByte()) != -1)
            cs.WriteByte((byte)data);

        fsIn.Close();
        cs.Close();
        fsCrypt.Close();

    }

FileStream fsInput = new FileStream(sInputFilename, 
                FileMode.Open, 
                FileAccess.Read);

FileStream fsEncrypted = new FileStream(sOutputFilename, 
                FileMode.Create, 
                FileAccess.Write);