关于登陆中的验证问题

[zhewky]

此程序中当验证用户名错误时，跳过了，小弟不才，不知道如何来验证，还有就是当我使用代码中注释掉的相对路径引用时，也会提示错误，不知道怎么办？希望高手们指教．本人初学Ｃ＃，很想入门，如果小弟有幸认识各位，小疵视为上帝所宠
MyQQ:253530133，谢谢各位的回复！
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Data.OleDb;
namespace WindowsApplication1
{
public partial class MyTest : Form
{
public MyTest()
{
InitializeComponent();
}

private void button2_Click(object sender, EventArgs e)
{
this.Close();
}

private void button1_Click(object sender, EventArgs e)
{
try
{
OleDbConnection conn = new OleDbConnection("Provider=Microsoft.Jet.OleDb.4.0;Data Source=e:\\exam.mdb");
// OleDbConnection conn = new OleDbConnection("Provider=Microsoft.Jet.OleDb.4.0;Data Source='" + Application.StartupPath + "'\\exam.mdb");
OleDbCommand comm = new OleDbCommand("select * from admin WHERE userid='"+this.textBox1.Text.Trim()+"'", conn);

conn.Open();

OleDbDataReader dr = comm.ExecuteReader();

while(dr!=null)
//if(dr.Read()!=null)
{
if(dr["userid"].ToString()==this.textBox1.Text.ToString())
//if (this.textBox1.Text.Equals(dr["userid"].ToString().Trim()))
{
if (dr["password"].ToString() == this.textBox2.Text.ToString())
//if (this.textBox2.Text.Equals(dr["password"].ToString().Trim()))
{
MessageBox.Show("你是合法用户");
}
else
{
MessageBox.Show("密码错误！");
this.textBox2.Focus();
this.textBox2.SelectAll();
}

}
else
{
MessageBox.Show("此用户不存在，是否注册！");
//this.textBox1.SelectAll();
}
}
conn.Close();

}
catch(Exception ee)
{

MessageBox.Show(AX.Message);
}


}
}
}

[amandag]

1.使用楼主所指用的路径，一般数据库文件放在和exe文件一个目录下，调试时对应的是debug目
录

2.你所使用的登录判断方式很容易被SQL 注入攻击

[amandag]

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Data.OleDb;

namespace WindowsApplication1
{
public class MyTest : Form
{
private System.Windows.Forms.TextBox textBox1;
private System.Windows.Forms.Button button1;
private System.Windows.Forms.Button button2;
private System.Windows.Forms.TextBox textBox2;
private System.ComponentModel.Container components = null;
public MyTest()
{
InitializeComponent();
}

protected override void Dispose( bool disposing )
{
if( disposing )
{
if (components != null)
{
components.Dispose();
}
}
base.Dispose( disposing );
}

#region Windows 窗体设计器生成的代码
/// <summary>
/// 设计器支持所需的方法 - 不要使用代码编辑器修改
/// 此方法的内容。
/// </summary>
private void InitializeComponent()
{
this.textBox1 = new System.Windows.Forms.TextBox();
this.textBox2 = new System.Windows.Forms.TextBox();
this.button1 = new System.Windows.Forms.Button();
this.button2 = new System.Windows.Forms.Button();
this.SuspendLayout();
//
// textBox1
//
this.textBox1.Location = new System.Drawing.Point(16, 80);
this.textBox1.Name = "textBox1";
this.textBox1.TabIndex = 0;
this.textBox1.Text = "";
//
// textBox2
//
this.textBox2.Location = new System.Drawing.Point(136, 80);
this.textBox2.Name = "textBox2";
this.textBox2.PasswordChar = '*';
this.textBox2.TabIndex = 1;
this.textBox2.Text = "";
//
// button1
//
this.button1.Location = new System.Drawing.Point(24, 168);
this.button1.Name = "button1";
this.button1.TabIndex = 2;
this.button1.Text = "button1";
this.button1.Click += new System.EventHandler(this.button1_Click);
//
// button2
//
this.button2.Location = new System.Drawing.Point(136, 168);
this.button2.Name = "button2";
this.button2.TabIndex = 3;
this.button2.Text = "button2";
this.button2.Click += new System.EventHandler(this.button2_Click);
//
// MyTest
//
this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);
this.ClientSize = new System.Drawing.Size(292, 273);
this.Controls.Add(this.button2);
this.Controls.Add(this.button1);
this.Controls.Add(this.textBox2);
this.Controls.Add(this.textBox1);
this.Name = "MyTest";
this.Text = "Form1";
this.ResumeLayout(false);

}
#endregion

/// <summary>
/// 应用程序的主入口点。
/// </summary>
[STAThread]
static void Main()
{
Application.Run(new MyTest());
}

private void button2_Click(object sender, EventArgs e)
{
this.Close();
}

private void button1_Click(object sender, EventArgs e)
{
try
{
// OleDbConnection conn = new OleDbConnection("Provider=Microsoft.Jet.OleDb.4.0;Data Source=e:\\exam.mdb");
OleDbConnection conn = new OleDbConnection("Provider=Microsoft.Jet.OleDb.4.0;Data Source=" + Application.StartupPath + @"\exam.mdb");
string str = "select * from admin WHERE userid='"+this.textBox1.Text.Trim()+"'";
OleDbCommand comm = new OleDbCommand(str, conn);

conn.Open();

OleDbDataReader dr = comm.ExecuteReader();

bool flag = false;
while(dr.Read())
{
if(dr["userid"].ToString()==this.textBox1.Text.ToString())
{
if (dr["password"].ToString() == this.textBox2.Text.ToString())
{
MessageBox.Show("你是合法用户");
}
else
{
MessageBox.Show("密码错误！");
this.textBox2.Focus();
this.textBox2.SelectAll();
}
flag = true;
}

}
if (flag==false)
MessageBox.Show("此用户不存在，是否注册！");

conn.Close();

}
catch(Exception ee)
{

MessageBox.Show(ee.Message);
}


}

}
}

[amandag]

1.拼Application.StartupPath 的时候，前后不该加单引号
OleDbConnection conn = new OleDbConnection("Provider=Microsoft.Jet.OleDb.4.0;Data Source=" + Application.StartupPath + @"\exam.mdb");

2.判断OleDbDataReader的对象dr是否还有记录用的是dr.Read()方法

3.只有遍历了数据库所有的记录，才能判断出用户是否存在，所以
MessageBox.Show("此用户不存在，是否注册！");应该放在循环之外

其他的小问题还很多，就不一一细说了

[zhewky]

高歌．首先谢谢你，那两天不是我的浏览器问题还是什么原因．我登陆不上来了，提示不正确的验证，可我的ID和密码及验证码都是正确的，不知道，我把浏览器又重新搞了一下．麻烦死了．说我的工作吧，我把你写的代码复制过去之后，它提示说MyTest前少了partial
我加上之后，又出现了七处错误说：按钮和文本已经声明？
（我把我的代码注释了）
如果方便留下您的联系方式吧（以消息形式发给我）或加我ＱＱ：253530133谢谢，以后向你多请教

[zhewky]

高歌，我怎么不能给你分哦！～
提示：你给的分的总和不对．．．．
不好意思，这时才结贴