运算符丢失是怎么回事

Dim cn As New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;" & _
 "Data Source=C:\Inetpub\wwwroot\WebApplication1\data\db1.mdb")
        cn.Open()
        Dim sql As String
        sql = "select UserName,PassWord,manage from denglu where UserName='" & TextBox1.Text & "' PassWord='" & TextBox2.Text & "'"
        Dim cmd As New OleDbCommand(sql, cn)
        Dim sdr As OleDbDataReader

        sdr = cmd.ExecuteReader()

        If (sdr.Read()) Then
            Session("users") = Me.TextBox1.Text
            Session("pass") = Me.TextBox2.Text

            Session("Role") = sdr.GetInt32(2)
            If Session("Role").ToString = "1" Then Response.Redirect("admin.aspx")
        Else
            Response.Redirect("main.aspx")
        End If


        Me.RegisterStartupScript("alert", "<script language='javascript'> alert('用户登陆失败,请重新输入!!')</script>")


        sdr.Close()

        cn.Close()
看着段代码有什么错误    谢谢