OleDb和ADO.NET讀取文本文件時進行條件查詢

OleDb 和ADO.NET讀取文本文件如何像一般的SQL查詢那樣進行條件查詢呢？文本文件沒有所謂的字段名稱，該怎麼處理呢？其實，在使用ADO.NET進行讀 取數據記錄的時候，在程序內部應該是有字段名稱來標識這些列的（具體的定義沒有找到官方的文檔，本文是採用實驗的方法得到的結論），那麼，怎麼知道列名是 什麼呢？下面的方法就可以很清楚地看到：

ASPX 代碼

<% @ Page Language = " C# " EnableViewState = " false " %>

<! DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" >
< script runat ="server" >
  protected void Page_Load(object sender, EventArgs e)
  {
    string ConnectionString;
    string SQLString;
    ConnectionString = " Provider=Microsoft.Jet.OLEDB.4.0;Data Source= " +
                        Server.MapPath( " ~ " ) + " ;Extended Properties=/"Text;HDR=No;FMT=Delimited/" " ;
    SQLString = " Select * from a.txt " ;
    System.Data.OleDb.OleDbConnection ConnectionText = new System.Data.OleDb.OleDbConnection();
    ConnectionText.ConnectionString = ConnectionString;
    ConnectionText.Open();
    System.Data.OleDb.OleDbDataAdapter AdapterText = new System.Data.OleDb.OleDbDataAdapter(SQLString, ConnectionText);
    System.Data.DataSet DataSetText = new System.Data.DataSet();
    AdapterText.Fill(DataSetText, " TextFile " );
    GridView1.DataSource = DataSetText;
    GridView1.DataBind();
    ConnectionText.Dispose();
  }

</ script >
< html xmlns ="http://www.w3.org/1999/xhtml" >
< head runat ="server" >
   < title > 孟憲會讀取文本文件測試 </ title >
</ head >
< body >
   < form id ="form1" runat ="server" >
   < asp:GridView ID ="GridView1" runat ="server" ShowHeader ="True" >
   </ asp:GridView >
   </ form >
</ body >
</ html >

可以看到如下的結果：

F1	F2	F3	F4	F5
2010/7/27 8:58:35	0.005	8	mxh	http://dotnet.aspx.cc
2010/7/27 8:58:36	0.005	2	mxh	http://dotnet.aspx.cc
2010/7/27 8:58:37	0.005	6	net_lover	http://dotnet.aspx.cc
2010/7/27 8:58:38	0.005	0	net_lover	http://dotnet.aspx.cc
2010/7/27 8:58:39	0.004	0	net_lover	http://dotnet.51aspx.com
2010/7/27 8:58:40	0.005	3	net_lover	http://dotnet.aspx.cc
2010/7/27 8:58:41	0.005	0	net_lover	http://dotnet.aspx.cc
2010/7/27 8:58:42	0.005	9	net_lover	http://dotnet.aspx.cc
2010/7/27 8:58:43	0.005	0	孟憲會	http://dotnet.51aspx.com
2010/7/27 8:58:44	0.005	0	孟憲會	http://dotnet.aspx.cc

好了，知道了列名，那麼按條件查詢應該是可以的，下面就進行下測試：

ASPX 代碼

<% @ Page Language = " C# " EnableViewState = " false " %>

<! DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" >
< script runat ="server" >
  protected void Page_Load(object sender, EventArgs e)
  {
    string ConnectionString;
    string SQLString;
    ConnectionString = " Provider=Microsoft.Jet.OLEDB.4.0;Data Source= " +
                        Server.MapPath( " ~ " ) + " ;Extended Properties=/"Text;HDR=No;FMT=Delimited/" " ;
    SQLString = " Select * from a.txt Where F1=#2010/7/27 8:58:36# " ;
    SQLString = " Select * from a.txt Where F2=0.006 " ;
    SQLString = " Select * from a.txt Where F4='孟憲會' And F5='http://dotnet.aspx.cc' " ;
    SQLString = " Select * from a.txt Where F4='孟憲會' " ;
    System.Data.OleDb.OleDbConnection ConnectionText = new System.Data.OleDb.OleDbConnection();
    ConnectionText.ConnectionString = ConnectionString;
    ConnectionText.Open();
    System.Data.OleDb.OleDbDataAdapter AdapterText = new System.Data.OleDb.OleDbDataAdapter(SQLString, ConnectionText);
    System.Data.DataSet DataSetText = new System.Data.DataSet();
    AdapterText.Fill(DataSetText, " TextFile " );
    GridView1.DataSource = DataSetText;
    GridView1.DataBind();
    ConnectionText.Dispose();
  }

</ script >
< html xmlns ="http://www.w3.org/1999/xhtml" >
< head runat ="server" >
   < title > 孟憲會讀取文本文件測試 </ title >
</ head >
< body >
   < form id ="form1" runat ="server" >
   < asp:GridView ID ="GridView1" runat ="server" ShowHeader ="False" >
   </ asp:GridView >
   </ form >
</ body >
</ html >

測試用的a.txt文件內容如下：
2010-7-27 8:58:35,0.005,8,mxh,http://dotnet.aspx.cc
2010-7-27 8:58:36,0.005,2,mxh,http://dotnet.aspx.cc
2010-7-27 8:58:37,0.005,6,net_lover,http://dotnet.aspx.cc
2010-7-27 8:58:38,0.005,0,net_lover,http://dotnet.aspx.cc
2010-7-27 8:58:39,0.004,0,net_lover,http://dotnet.51aspx.com
2010-7-27 8:58:40,0.005,3,net_lover,http://dotnet.aspx.cc
2010-7-27 8:58:41,0.005,0,net_lover,http://dotnet.aspx.cc
2010-7-27 8:58:42,0.006,9,net_lover,http://dotnet.aspx.cc
2010-7-27 8:58:43,0.005,0,孟憲會,http://dotnet.51aspx.com
2010-7-27 8:58:44,0.005,0,孟憲會,http://dotnet.aspx.cc

注意：日期格式可能根據系統的設置有所不同，這點需要注意。