public bool ExportToCsv(DataSet src, string fileName)

    {

        StreamWriter writer = null;

        fileName = Server.MapPath("Test") + "//" + fileName;

        try

        {

            if (src == null || src.Tables.Count == 0) throw new Exception("dataset is null or has not table in dataset");

     

            for (int i = 0; i < src.Tables.Count; i++)

            {

                if (i > 0)

                    fileName = fileName.Substring(0, fileName.IndexOf('.')) + i + fileName.Substring(fileName.IndexOf("."));



                writer = new StreamWriter(fileName);

                DataTable dt = src.Tables[i];

                StringBuilder sb = new StringBuilder();

                for (int j = 0; j < dt.Columns.Count; j++)

                {

                    string colName = dt.Columns[j].ColumnName;

                    if (colName.IndexOf(',') > -1)

                        colName = colName.Insert(0, "/"").Insert(colName.Length + 1, "/"");

                    sb.Append(colName);

                    if (!colName.Equals(""))

                        if (j != dt.Columns.Count - 1)

                            sb.Append(",");

                }

                writer.WriteLine(sb.ToString());

                sb = new StringBuilder();

                string temp = "";

                for (int j = 0; j < dt.Rows.Count; j++)

                {

                    DataRow dr = dt.Rows[j];

                    for (int k = 0; k < dt.Columns.Count; k++)

                    {

                        object o = dr[k];

                        if (o != null)

                            temp = o.ToString();

                        if (temp.IndexOf(',') > -1)

                            temp = temp.Insert(0, "/"").Insert(temp.Length + 1, "/"");

                        sb.Append(temp);

                        if (k != dt.Columns.Count - 1)

                            sb.Append(",");

                    }

                    writer.WriteLine(sb.ToString());

                    sb = new StringBuilder();

                }

                writer.Close();

            }

        }

        catch (Exception ex)

        {

            throw new Exception("Save csv error", ex);

        }

        finally

        {

            if (writer != null) writer.Close();

        }

        return true;

    }