C# 与 OleDbConnection 连接
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Connect with OleDbConnection
提问by asguy
I am trying to connect to a database with two tables. However, after I try and log in, I have an error. The error says there is no row at spot zero. I think this is because of my connection:
我正在尝试连接到具有两个表的数据库。但是，在我尝试登录后，出现错误。错误说零点没有行。我认为这是因为我的联系：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.OleDb;
namespace Project3
{
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void login_Click(object sender, EventArgs e)
{
OleDbConnection connect = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Users\parodeghero\Documents\Visual Studio 2010\Projects\Project3\Project3\App_Data\QA.mdb;Persist Security Info=True");
//set up connection string
OleDbCommand command = new OleDbCommand("select * from Employee where Login=@login", connect);
OleDbParameter param0 = new OleDbParameter("@login", OleDbType.VarChar);
param0.Value = employeeID.Text;
command.Parameters.Add(param0);
//middle tier to run connect
OleDbDataAdapter da = new OleDbDataAdapter(command);
DataSet dset = new DataSet();
da.Fill(dset);
//problem line
if (dset.Tables[0].Rows[0]["Password"].ToString().Equals(password.Text))
{
采纳答案by Lyuben Todorov
You need to open the connection
你需要打开连接
protected void login_Click(object sender, EventArgs e)
{
OleDbConnection connect = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Users\parodeghero\Documents\Visual Studio 2010\Projects\Project3\Project3\App_Data\QA.mdb;Persist Security Info=True");
//set up connection string
OleDbCommand command = new OleDbCommand("select * from Employee where Login=@login", connect);
OleDbParameter param0 = new OleDbParameter("@login", OleDbType.VarChar);
param0.Value = employeeID.Text;
command.Parameters.Add(param0);
try
{
connect.Open();
}catch(Exception err){ Debug.WriteLine(err.Message);}
//middle tier to run connect
OleDbDataAdapter da = new OleDbDataAdapter(command);
DataSet dset = new DataSet();
da.Fill(dset);
回答by JRT
You do NOT need to open the connection. OleDbDataAdapter.Fill will open the connection AND close it if it found it closed to start with. Fill leaves the connection in the state that it finds it.
您不需要打开连接。OleDbDataAdapter.Fill 将打开连接并关闭它，如果它发现它开始关闭。Fill 将连接保持在它找到它的状态。
I do question your SQL. My understanding of OleDb is that it does NOT support naming parameters in SQL. It needs a place holder "?" instead of @login. You need a Parameter for each placeholder and the parameters must be added in the order they occurr. If your SQL is not valid, then you will have either a SQL Exception or no data in the DataTable, i.e. NO row 0 !
我确实质疑您的 SQL。我对 OleDb 的理解是它不支持 SQL 中的命名参数。它需要一个占位符“？” 而不是@login。每个占位符都需要一个参数，并且必须按照参数出现的顺序添加参数。如果您的 SQL 无效，那么您将有 SQL 异常或 DataTable 中没有数据，即没有第 0 行！
回答by curos
oledb connection complete code
oledb连接完整代码
http://csharp.net-informations.com/data-providers/csharp-oledb-connection.htm
http://csharp.net-informations.com/data-providers/csharp-oledb-connection.htm
string connetionString = null;
OleDbConnection cnn ;
connetionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=yourdatabasename.mdb;";
cnn = new OleDbConnection(connetionString);
try
{
cnn.Open();
MessageBox.Show ("Connection Open ! ");
cnn.Close();
}
catch (Exception ex)
{
MessageBox.Show("Can not open connection ! ");
}
curos
古罗斯
