public DataTable GetTableFromExcel(string sheetName, string filePath)
        {
            const string connStrTemplate = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source={0};Extended Properties=Excel 8.0;";
            DataTable dt = null;
            if (!System.IO.File.Exists(filePath))
            {
                // don't find file
                return null;
            }
            OleDbConnection conn = new OleDbConnection(string.Format(connStrTemplate, filePath));
            try
            {
                conn.Open();
                if (sheetName == null || sheetName.Trim().Length == 0)
                {
                    DataTable schemaTable = conn.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, null);
                    sheetName = schemaTable.Rows[0]["TABLE_NAME"].ToString().Trim();
                }
                else
                {
                    sheetName += "$";
                }

                string strSQL = "Select * From [" + sheetName + "]";
                OleDbDataAdapter da = new OleDbDataAdapter(strSQL, conn);
                DataSet ds = new DataSet();
                da.Fill(ds);
                dt = ds.Tables[0];
            }
            catch(Exception ex)
            {
                throw ex;
            }
            return dt;
        }