请帮我看看这段代码错在哪里？：报错

 Private Sub OK_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles OK.Click

         Public objConnection As New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=F:\Visual Studio 2008\采购验收单.mdb")
       Public objCommand As OleDbCommand

       Dim Rd As OleDb.OleDbDataReader

        If txtPassWord.Text.Trim = "" Then
            lblWarning.Text = "您还没有输入密码！"
            Exit Sub
        End If
        Dim strSQL As String
        strSQL = "SELECT 用户名 FROM [User] where 用户名 ='" & cmbUserName.Text.ToString & "' and 密码 = '" & txtPassWord.Text.ToString & "'"

        '打开与数据库的连接
        objConnection.Open()

        objCommand = New OleDbCommand(strSQL, objConnection)

        Rd = objCommand.ExecuteReader()

        If Rd.Read Then
            lblWarning.Text = String.Empty
            objConnection.Close()
            Rd.Close()
            Me.Hide()
            frmMain.ShowDialog()
        Else
            txtPassWord.Text = ""
            txtPassWord.Focus()
            lblWarning.Text = "密码不正确，请重新输入！"
            objConnection.Close()
            Rd.Close()
            Exit Sub
        End If