DataTable 与 Excel文件（CSV）相互转化

在一个项目中，需要从Excel文件导入数据然后再datagridview上显示，同时也需要右键datagridview时可以将数据另存为excel文件，于是写了这两个工具方法。本文提供了两个方法用于Excel和DataTable之间相互转化。

1， 从Excel文件、CSV文件导入到DataTable：
 

public static DataTable csvToDataTable(string file)
 {
     string strConn = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + file + ";Extended Properties='Excel 8.0;'"; // Excel file
 if(file.EndsWith(".csv"))
         strConn = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + path + ";Extended Properties='TEXT;HDR=Yes;FMT=Delimited;'"; // csv file:HDR=Yes-- first line is header
     OleDbConnection oleConn = new OleDbConnection(strConn);
     oleConn.Open();
     DataTable sheets = oleConn.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, null);
     if (sheets == null || sheets.Rows.Count < 1)
     {
         return null;
     }
     String fileName = sheets.Rows[0]["TABLE_NAME"].ToString(); // sheets.Rows[0] -- first sheet of excel
 if(file.EndsWith(".csv"))
  fileName = file.Substring(file.LastIndexOf("/"));
     string olestr = "select * from [" + fileName + "]";
     if (file.EndsWith(".csv"))
         olestr = "select * from [" + fileName + "]";
     OleDbCommand oleComm = new OleDbCommand(olestr, oleConn);
     oleComm.Connection = oleConn;
     OleDbDataAdapter oleDa = new OleDbDataAdapter();
     oleDa.SelectCommand = oleComm;
     DataSet ds = new DataSet();
     oleDa.Fill(ds);
     oleConn.Close();
     return ds.Tables[0];
 }

2，DataTable到出到CSV文件：
 

public static void dataTableToCsv(DataTable table, string file)
        {
            string title = "";

            FileStream fs = new FileStream(file, FileMode.Create);
            StreamWriter sw = new StreamWriter(new BufferedStream(fs), System.Text.Encoding.Default);

            for (int i=0; i<table.Columns.Count; i++)
            {
                title += table.Columns[i].ColumnName + ",";
            }
            title = title.Substring(0, title.Length - 1) + "\n";
            sw.Write(title);

            foreach (DataRow row in table.Rows)
            {
                string line = "";
                for (int i = 0; i < table.Columns.Count; i++)
                {
                    line += row[i].ToString() + ",";
                }
                line = line.Substring(0, line.Length - 1) + "\n";

                sw.Write(line);
            }

            sw.Close();
            fs.Close();
        }
    }