登录验证问题

  Protected Sub Page_Load(sender As Object, e As EventArgs)
        If Request.Cookies("username") Is Nothing Or Request.Cookies("userpass") Is Nothing Or Request.Cookies("username").Value = "" Or Request.Cookies("userpass").Value = "" Then
            Response.Redirect("~/login.aspx")
            Return
        End If
        Dim username As String = Request.Cookies("username").Value
        Dim userpass As String = Request.Cookies("userpass").Value
        'If username = "" Or userpass = "" Then
        '    Response.Redirect("~/login.aspx")
        '    Return
        'End If
        Dim sds As SqlDataSource = New SqlDataSource("Data Source=.;Initial Catalog=mydata;User ID=sa;Password=Abcdefg1", "select b from t_user where username = @username and userpass = @userpass")
        sds.SelectParameters.Add("username", username)
        sds.SelectParameters.Add("userpass", userpass)
        Dim dv As System.Data.DataView = sds.Select(DataSourceSelectArguments.Empty)
        Dim i As Integer = dv(0)(0)
        If i = 0 Then
            Response.Redirect("~/Default.aspx")
            Return
        End If
    End Sub