Format excel cells via code behind

I have a routine that generates an excel spreadsheet from an Oracle database. What happens is that in BD I have values like this: 3456.90 or 1900.00 When these values arrive in the worksheet, it looks like this: 3456,90 or 1900

that is, when the value has the last two digits after the dot, with value 00, in the worksheet shows an integer. Because this is a report, the worksheet must already have the formatted values and not the user manually formatted. What can I do? It is exported in .csv format. Is there any way to do this? In my Page Load looks like this:

protected void Page_Load(object sender, EventArgs e)
        {
            var conexao = ConfigurationManager.ConnectionStrings["TS"].ConnectionString;
            var connectionOracle = new OracleConnection(conexao);
            connectionOracle.Open();
            var cmd = new OracleCommand(sql(), connectionOracle);
            OracleDataReader odr = cmd.ExecuteReader();
            ItemMatMed itemMatMed = new ItemMatMed();

            try
            {
                Response.Write("Data de Inclusão;Tipo de Tabela;Tabela;Codigo;TUSS;Descrição;Fabricante;Referência do Fabricante;Registro ANVISA;Classificação SIMPRO;Grupo Mat/Med;Grupo Estatístico;Autorização Prévia;Última Vigência;Valor;Tabela Própria;");
                Response.Write("\r");

                while (odr.Read())
                {
                    Response.Write(odr[0].ToString() + ";" + odr[1].ToString() + ";" + odr[2].ToString() + ";" + odr[3].ToString() + ";" + odr[4].ToString() + ";" +
                                   odr[5].ToString() + ";" + odr[6].ToString() + ";" + odr[7].ToString() + ";" + odr[8].ToString() + ";" + odr[9].ToString() + ";" +
                                   odr[10].ToString() + ";" + odr[11].ToString() + ";" + odr[12].ToString() + ";" + odr[13].ToString() + ";" + odr[14].ToString() + ";");  

                    Response.Write("\r");
                }
            }
            finally
            {
                cmd.Dispose();
                connectionOracle.Close();
                connectionOracle.Dispose();
            }

            Response.ContentType = "text/plain";
            Response.AppendHeader("Content-Disposition","attachment; filename=relacao_materiais.csv");
            Response.End();
        }