Visual Basic 6.0登录表单

我在创建登录表单时遇到问题。我的表单已连接到我的ora10g数据库。用户名在一个组合框中，这样用户就可以轻松登录。有人能帮我吗？为什么每次我在组合框中选择用户名并键入该用户名的正确密码时，它总是显示消息框"用户名无效"。谢谢你们的帮助！

这是我的OK按钮代码：

    Dim cnn As New ADODB.Connection
    Set cnn = New ADODB.Connection
    cnn.Open " provider = MSDAORA; user id = System; password = Estacio;"
    Dim rs As ADODB.Recordset
    Set rs = New ADODB.Recordset
    rs.Open "Select * From Admin Where Username = '" & Combo1.Text & "'", cnn
    If rs.RecordCount < 1 Then
    MsgBox "Username is Invalid. Please try again.", vbInformation
    Combo1.SetFocus
    Else
    If txtPassword.Text = rs!Password Then
    Timer1.Enabled = True
    ProgressBar1.Visible = True
    Else
    MsgBox "Password is Invalid. Please try again.", vbInformation
    txtPassword.SetFocus
    Exit Sub
    End If
    End If
    Set rs = Nothing
    End Sub

 Dim cn As OracleConnection = New OracleConnection("Data Source=xe;User ID=hr;password=hr;Unicode=True")
    Dim cmd As OracleCommand
    Dim dr As OracleDataReader
cmd .Connection = cn
            cmd .CommandText = "SELECT COUNT(1) FROM Admin WHERE username = @username AND password = @password"
            cn.Open()
          cmd .Parameters.Add(New SqlClient.SqlParameter("@username", Combo1.Text))
            cmd .Parameters.Add(New SqlClient.SqlParameter("@password", txtPassword.Text))
 If cmd .ExecuteScalar = 1 Then
                MsgBox("Successful Login")
            Else
                MsgBox("Try Again")
            End If