How To Compare Identity.name To Another Database

Here's my scenario.  I've got an web site that is going to allow access across two different domains.  So I pull out the user name and domain with a split.  At that point I want to say If user name = a value in bug_user table then redirect ~default.aspx Else redirect to other page.  I'm kind of stuck.  Here is what I got so far.  
 Imports System.Data
Imports System.Data.SqlClient
Partial Class MasterPage
    Inherits System.Web.UI.MasterPage

    Sub page_load()

        Dim user As System.Security.Principal.IPrincipal
        user = System.Web.HttpContext.Current.User

        Dim username As String
        username = user.Identity.Name

        Dim namer As String
        Dim domain As String
        Dim firstname As String


        namer = username.Split("")(1)
        domain = username.Split("")(0)


        Dim objcon As ConnectionStringSettings = ConfigurationManager.ConnectionStrings("bug_trackerConnectionString")
        Dim str As String = objcon.ConnectionString
        Dim con As New SqlConnection(str)
        Dim com As New SqlCommand("", con)

??????????????????????????
        con.Open()
             com.commandText = "Select FirstName, LastName, Userid, Domain from bug_user"
        con.Close()

??????????????????????? 
Between the question marks is where i start to get lost.  I don't know how to look into the column Userid in the table bug_user table to see if my variable namer is present and I don't know where I should start my if statement.  Thank for your help.