1.在导出的时候，拼出cvs串：数字直接逗号分隔，字符要加引号
"\""+indexdata.DataValue.ToString()+ "\"," + "\r\n";  换行
写入文件的时候用下面的写法没问题，不然会出现：不根据逗号分开，excel打开文件串存储在一个column中。
using (StreamWriter sw = new StreamWriter(filePath))
{
sw.Write(GenerateExportString());
sw.Close();
}

2.导入写法

public DataSet ConnectCSVFile(string fileName ,string path)
{
System.Data.Odbc.OdbcDataAdapter obj_oledb_da;
DataSet ds = new DataSet();
try
{
string strConnString="Driver={Microsoft Text Driver (*.txt; *.csv)};Dbq="+path.Trim()+";Extensions=asc,csv,tab,txt;Persist Security Info=False";
string sql_select;
System.Data.Odbc.OdbcConnection conn; 
//Create connection to CSV file
conn = new System.Data.Odbc.OdbcConnection(strConnString.Trim());
// For creating a connection using DSN, use following line
//conn = new System.Data.Odbc.OdbcConnection(DSN="MyDSN");
//Open the connection
conn.Open();
//Fetch records from CSV
sql_select = "select * from ["+ fileName +"]";
obj_oledb_da = new System.Data.Odbc.OdbcDataAdapter(sql_select,conn);
//Fill dataset with the records from CSV file
obj_oledb_da.Fill(ds,"dc_indexdata");
//Close Connection to CSV file
conn.Close();
}
catch(Exception er) //Error
{DcService.MessageService.ShowError(er.Message);}
return ds;
}