Question

我正在使用此代码：

Dim con As OleDbConnection = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source= UserPass.mdb;")
con.Open()
Dim str As String
str = "SELECT * FROM UserPass WHERE Username='" & txtUsername.Text & "' AND Password='" & txtPassword.Text & "'"
Dim cmd As OleDbCommand = New OleDbCommand(str, con)
cmd.Parameters.AddWithValue("user", txtUsername.Text)
cmd.Parameters.AddWithValue("pass", txtPassword.Text)
Dim sdr As OleDbDataReader = cmd.ExecuteReader()
' It will be case sensitive if you compare usernames here.   
If sdr.HasRows Then
    If sdr.Read Then
        If txtPassword.Text <> sdr("Password").ToString And txtUsername.Text <> sdr("Username").ToString Then
            MessageBox.Show(" Incorrect Username/Password. Login Denied ", " Error! ", MessageBoxButtons.OK, MessageBoxIcon.Error)
        Else
            MessageBox.Show(" You are now Logged In! ", " Welcome! ", MessageBoxButtons.OK, MessageBoxIcon.Asterisk)
            frmOne.Show()
            Me.Hide()
        End If
    End If
End If
sdr.Close()
con.Close()

这是应该检查字母大小写的行，但它似乎不起作用：

If txtPassword.Text <> sdr("Password").ToString And txtUsername.Text <> sdr("Username").ToString Then

Answer 1

除非我误解了if语句中的And，否则您使用的逻辑只会在用户名和密码不匹配时拒绝登录。如果密码不匹配，但用户没有，则会切换到else块并将用户登录。

尝试将其更改为：

If txtPassword.Text <> sdr("Password").ToString Or txtUsername.Text <> sdr("Username").ToString Then

区分大小写的用户名和密码

1 个答案: