how do i solve null referce variable

Imports System.Data.OleDb

Partial Class Default2
    Inherits System.Web.UI.Page

    Private Property UserName As Object

    Private Property auth As Boolean



    Private Property txtPwd As Object

    Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim connString As String = "Data Source=C:\Users\Administrator\Desktop\login.mdb;Provider=Microsoft.Jet.OleDb.4.0"
        Dim qryString As String = "SELECT username, password FROM login;"
        Dim objConn As New OleDbConnection(connString)
        Dim objCmd As New OleDbCommand(qryString, objConn)
        Dim myReader As OleDbDataReader

        Try

            Dim gotUser As Boolean = False
            objConn.Open()
            myReader = objCmd.ExecuteReader

            While myReader.Read
               .. If myReader.Item("username") = UserName.Text Then.. ' This is the error line
                    gotUser = True
                    auth = CheckPwd(myReader.Item("username"), myReader.Item("password"))
                End If

            End While
            If gotUser = False Then
                Label3.Text = "You are not authorized for access"
            Else
                Select Case auth
                    Case True
                        FormsAuthentication.RedirectFromLoginPage(UserName.Text, False)
                    Case Else
                        Label3.Text = "Incorrect Password"
                End Select
            End If

        Catch ex As Exception

            Label3.Text = ex.ToString

        Finally
            objConn.Close()
        End Try
        
    End sub

    Public Function CheckPwd(ByVal username As String, ByVal password As String) As Boolean

        Dim Authorized As Boolean = False
        Dim pwdFromUser As String = txtPwd.Text

        If pwdFromUser = password Then
            Authorized = True
        Else
            Authorized = False
        End If

        Return Authorized

    End Function

End Class

System.NullReferenceException: Object variable or With block variable not set. at Microsoft.VisualBasic.CompilerServices.Symbols.Container..ctor(Object Instance) at Microsoft.VisualBasic.CompilerServices.NewLateBinding.LateGet(Object Instance, Type Type, String MemberName, Object[] Arguments, String[] ArgumentNames, Type[] TypeArguments, Boolean[] CopyBack) at Default2.Button1_Click(Object sender, EventArgs e) in C:\Users\Administrator\Documents\Visual Studio 2010\WebSites\WebSite9\Default2.aspx.vb:line 28