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vb.net密码验证,如何用vb制作登录系统验证码
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VB.NET用户登录，账号密码正确，却提示密码错误！
Private Sub BtOk_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Btok.Click
Dim con As OleDbConnection = New OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=Admin.accdb;Persist Security Info=True")
Dim com As OleDbCommand = New OleDbCommand("select * from 用户名", con)
con.Open()
Dim h1 As OleDbDataReader
Dim table As New DataTable
h1 = com.ExecuteReader()
table.Load(h1)
If txtName.Text = "" Then
MsgBox("请输入用户名", MsgBoxStyle.OkCancel + MsgBoxStyle.Exclamation, "错误提示")
ElseIf txtName.Text "" And txtPasswd.Text = "" Then
MsgBox("请输入密码", MsgBoxStyle.OkCancel + MsgBoxStyle.Exclamation, "错误提示")
ElseIf table.Select("用户名='" txtName.Text "'").Length 0 Then
If table.Select("用户名='" txtName.Text "'")(0)("密码").ToString = txtPasswd.Text Then
MsgBox("成功登陆", MsgBoxStyle.OkCancel + MsgBoxStyle.Exclamation, "错误提示") Then
Form1.Show()
Me.Visible = False
Exit Sub
Else
MsgBox("密码错误", MsgBoxStyle.OkCancel + MsgBoxStyle.Exclamation, "错误提示")
End If
Else
MsgBox("用户名不存在", MsgBoxStyle.OkCancel + MsgBoxStyle.Exclamation, "错误提示")
Exit Sub
End If
table.Clear()
h1.Close()
con.Close()
End Sub
相关问答
Q1: VB.NET登陆界面。要验证登录用户名和密码是否正确。登陆后有管理员和普通用户权限判断。管理员只能登录一
将用户名，密码，用户类型存在数据库中，登陆时比较输入的值是否与数据库相同即可。
Q2: VB.net 如何实现记住密码 自动登录
代码如下：
/// summary
/// 连接到窗体：通过密码保护信息找回密码！
/// /summary
/// param name="sender"/param
/// param name="e"/param
private void lbl_mibao_Click(object sender, EventArgs e)
{
Getbackpwd getbackpwd = new Getbackpwd();
getbackpwd.Show();
}
/// summary
/// 当该窗体加载时从xml文件中读取用户信息并加载到combox的Items中
/// /summary
/// param name="sender"/param
/// param name="e"/param
private void Addresslist_Load(object sender, EventArgs e)
{
XmlTextReader reader = new XmlTextReader(@"E:\面向对象--C#练习\通讯录\address list\address list\user.xml");
while (reader.Read())
{
//if (reader.LocalName.Equals("Name") || reader.LocalName.Equals("Number"))
if (reader.LocalName.Equals("username"))
{
this.cmbUserName.Items.Add(reader.ReadString());
}
//if (reader.LocalName.Equals("Number"))
//{
// this.label2.Text += reader.ReadString() + "\n";\
//}
}
reader.Close();
}
/// summary
/// 保存用户名到user.xml
/// /summary
//在listcontol上更改SelectedValue时执行从数据库读取密码的事件
private void cmbUserName_SelectedValueChanged(object sender, EventArgs e)
{
string username = cmbUserName.Text.Trim();
string sql = string.Format("select pwd from Admin where Username='{0}'", username);
try
{
SqlCommand command = new SqlCommand(sql, DBHelper.connection);
DBHelper.connection.Open();
SqlDataReader dataReader = command.ExecuteReader();
while (dataReader.Read())
{
txtpwd.Text = (string)dataReader["pwd"];
checkBoxpwd.Checked = true;
}
}
catch
{
MessageBox.Show("数据库操作出错！");
}
finally
{
DBHelper.connection.Close();
}
}
/// summary
/// 记住密码操作
/// /summary
/// param name="sender"/param
/// param name="e"/param
private void checkBoxpwd_Enter(object sender, EventArgs e)
{
bool check = true;
check = checkinput(cmbUserName.Text.Trim());
if ((string)cmbUserName.Text.Trim() == "")
{
MessageBox.Show("请输入用户名", "输入提示", MessageBoxButtons.OK, MessageBoxIcon.Information);
cmbUserName.Focus();
}
else
{
if (txtpwd.Text.Trim() == "")
{
MessageBox.Show("请输入密码", "输入提示", MessageBoxButtons.OK, MessageBoxIcon.Information);
txtpwd.Focus();
}
else
{
bool isValidUser = false; // 标识是否为合法用户
string message = ""; // 如果登录失败，显示的消息提示
// 如果验证通过，就显示相应的用户窗体，并将当前窗体设为不可见
if (ValidateInput())
{
// 调用用户验证方法
isValidUser = ValidateUser(cmbUserName.Text, txtpwd.Text, ref message);
// 如果是合法用户，显示相应的窗体
if (isValidUser)
{
if (check == true)
{
XmlDocument doc = new XmlDocument();
doc.Load(@"E:\面向对象--C#练习\通讯录\address list\address list\user.xml");//(@"E:\面向对象--C#练习\通讯录\address list\address list\user.xml");
XmlElement node = doc.CreateElement("user");
XmlNode xnode = (XmlNode)doc.CreateElement("username");
xnode.InnerText = cmbUserName.Text.Trim();
node.AppendChild(xnode);
doc.DocumentElement.InsertAfter(node, doc.DocumentElement.LastChild);
doc.Save(@"E:\面向对象--C#练习\通讯录\address list\address list\user.xml");
//doc.Load (@"E:\面向对象--C#练习\通讯录\address list\address list\user.xml");
}
}
// 如果登录失败，显示相应的消息
else
{
MessageBox.Show(message, "记住密码失败！", MessageBoxButtons.OK, MessageBoxIcon.Information);
}
}
}
}
}
/// summary
/// 验证当前combox中内容是否已经存在于xml文件中
/// /summary
/// param name="text"/param
/// returns/returns
private bool checkinput(string text)
{
int count;
bool c = true;
for (count = 0; count cmbUserName.Items.Count;count ++ )
{
if (text ==(string )cmbUserName .Items [count])
{
c=false;
}
}
return c;
}
xml文件内容如下：?xml version="1.0" encoding="utf-8"?
person
user
Q3: VB.NET程序加密问题
在FormLoad事件里，写如下代码：
If MsgBox("是否打开程序?", MsgBoxStyle.OkCancel) = MsgBoxResult.Cancel Then
End
End If
大概方法是这样，要想加密码的话，将MsgBox()换成你自己写的对话框。
如果还嫌不够具体的话，你这点儿分就不够。。。
