.NET读取Excel文件的三种方法的区别

public DataSet ExcelToDS(string Path)  
{   
　　string strConn = "Provider=Microsoft.Jet.OLEDB.4.0;" +"Data Source="+ Path +";"+"Extended Properties=Excel 8.0;";
   OleDbConnection conn = new OleDbConnection(strConn);   
　　conn.Open();
   string strExcel = "";
   OleDbDataAdapter myCommand = null;
   DataSet ds = null;
   strExcel="select * from [sheet1$]";
   myCommand = new OleDbDataAdapter(strExcel, strConn);
   ds = new DataSet();    myCommand.Fill(ds,"table1");
   return ds;
}

string strConn = "Provider=Microsoft.Jet.OLEDB.4.0;" +"Data Source="+ Path +";"+"Extended Properties=Excel 8.0;";
OleDbConnection conn = new OleDbConnection(strConn);
DataTable schemaTable = objConn.GetOleDbSchemaTable(System.Data.OleDb.OleDbSchemaGuid.Tables,null);
string tableName=schemaTable.Rows[0][2].ToString().Trim();  

public void DSToExcel(string Path,DataSet oldds)   {   
//先得到汇总Excel的DataSet 主要目的是获得Excel在DataSet中的结构   
string strCon = " Provider = Microsoft.Jet.OLEDB.4.0 ; Data Source ="+path1+";Extended Properties=Excel 8.0" ;
OleDbConnection myConn = new OleDbConnection(strCon) ;
string strCom="select * from [Sheet1$]";
myConn.Open ( ) ;
OleDbDataAdapter myCommand = new OleDbDataAdapter ( strCom, myConn ) ;
ystem.Data.OleDb.OleDbCommandBuilder builder=new OleDbCommandBuilder(myCommand);   
//QuotePrefix和QuoteSuffix主要是对builder生成InsertComment命令时使用。   
builder.QuotePrefix="[";     //获取insert语句中保留字符（起始位置）
builder.QuoteSuffix="]"; //获取insert语句中保留字符（结束位置） 
DataSet newds=new DataSet();
myCommand.Fill(newds ,"Table1") ;
for(int i=0;i<oldds.Tables[0].Rows.Count;i++)   
{    
　　//在这里不能使用ImportRow方法将一行导入到news中，
　　//因为ImportRow将保留原来DataRow的所有设置(DataRowState状态不变)。
　　//在使用ImportRow后newds内有值，但不能更新到Excel中因为所有导入行的DataRowState!=Added
　　DataRow nrow=aDataSet.Tables["Table1"].NewRow();
   for(int j=0;j<newds.Tables[0].Columns.Count;j++)
   {     
　　　　nrow[j]=oldds.Tables[0].Rows[i][j];
   }    
　　　　newds.Tables["Table1"].Rows.Add(nrow);  
}   
myCommand.Update(newds,"Table1");
myConn.Close();
}

//读取EXCEL的方法   (用范围区域读取数据)
private void OpenExcel(string strFileName)  {     
object missing = System.Reflection.Missing.Value;     
Application excel = new Application();//lauch excel application
if (excel == null)    
{       
  Response.Write("<script>alert('Can't access excel')</script>");     
}    
else    
{         
　　excel.Visible = false;
　　excel.UserControl = true;          // 以只读的形式打开EXCEL文件
    Workbook wb = excel.Application.Workbooks.Open(strFileName, missing, true, missing, missing, missing,missing, missing, missing, true, missing, missing, missing, missing, missing);          //取得第一个工作薄 
    Worksheet ws = (Worksheet)wb.Worksheets.get_Item(1);           //取得总记录行数   (包括标题列)   
   int rowsint = ws.UsedRange.Cells.Rows.Count; //得到行数         
　　//int columnsint = mySheet.UsedRange.Cells.Columns.Count;//得到列数          
　　//取得数据范围区域  (不包括标题列)
   Range rng1 = ws.Cells.get_Range("B2", "B" + rowsint);   //item         
   Range rng2 = ws.Cells.get_Range("K2", "K" + rowsint);  //Customer         
　 object[,] arryItem= (object[,])rng1.Value2;   //get range's value        
   object[,] arryCus = (object[,])rng2.Value2;             //将新值赋给一个数组        
   string[,] arry = new string[rowsint-1, 2];         
  for (int i = 1; i <= rowsint-1; i++)        
  {             
　　  //Item_Code列             
　　 arry[i - 1, 0] =arryItem[i, 1].ToString();              //Customer_Name列            
 　　arry[i - 1, 1] = arryCus[i, 1].ToString();       
  }      
  Response.Write(arry[0, 0] + "  /  " + arry[0, 1] + "#" + arry[rowsint - 2, 0] + "  /  " + arry[rowsint - 2, 1]);      }      
  excel.Quit(); 
　excel = null;  
  Process[] procs = Process.GetProcessesByName("excel"); 
foreach (Process pro in procs)     
{         
　　pro.Kill();//没有更好的方法,只有杀掉进程    
}     
GC.Collect(); 
}

using System.Text;和using System.IO;           
FileStream fs = new FileStream("d:\\Customer.csv", FileMode.Open, FileAccess.Read, FileShare.None);
StreamReader sr = new StreamReader(fs, System.Text.Encoding.GetEncoding(936));
string str = "";           
string s = Console.ReadLine();           
while (str != null)           
{   
　　str = sr.ReadLine();
　　string[] xu = new String[2];
　　xu = str.Split(',');
　　string ser = xu[0];
　　string dse = xu[1];
　　if (ser == s)
　　{ 
　　　　Console.WriteLine(dse);break;
　　}          
}  
sr.Close();

//txt文件名 
string fn = DateTime.Now.ToString("yyyyMMddHHmmss") + "-" + "PO014" + ".txt";   OleDbConnection con = new OleDbConnection(conStr);   con.Open();  string sql = "select  ITEM,REQD_DATE,QTY,PUR_FLG,PO_NUM from TSD_PO014";          OleDbCommand mycom = new OleDbCommand("select * from TSD_PO014", mycon); 
//OleDbDataReader myreader = mycom.ExecuteReader();  //也可以用Reader读取数据
DataSet ds = new DataSet(); 
OleDbDataAdapter oda = new OleDbDataAdapter(sql, con);
oda.Fill(ds, "PO014"); 
DataTable dt = ds.Tables[0]; 
FileStream fs = new FileStream(Server.MapPath("download/" + fn), FileMode.Create, FileAccess.ReadWrite); 
StreamWriter strmWriter = new StreamWriter(fs);    //存入到文本文件中   
//把标题写入.txt文件中 
//for (int i = 0; i <dt.Columns.Count;i++) 
//{ 
//    strmWriter.Write(dt.Columns[i].ColumnName + "  ");
//} 
foreach (DataRow dr in dt.Rows) 
{    
　　string str0, str1, str2, str3;     
　　string str = "|";  //数据用"|"分隔开   
　　str0 = dr[0].ToString();     
　　str1 = dr[1].ToString();   
　　str2 = dr[2].ToString(); 
　　str3 = dr[3].ToString();  
   str4 = dr[4].ToString().Trim();  
   strmWriter.Write(str0);  
   strmWriter.Write(str); 
   strmWriter.Write(str1);  
   strmWriter.Write(str); 
   strmWriter.Write(str2);  
   strmWriter.Write(str);  
   strmWriter.Write(str3); 
   strmWriter.WriteLine();  //换行 
} 
strmWriter.Flush();
strmWriter.Close();
if (con.State == ConnectionState.Open) 
{    
　　con.Close();
}