มันขึ้นว่าObject reference not set to an instance of an object.ทำไงครับ vb

Imports System.Data
Imports System.Data.OleDb


Public Class Form1

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim conStr As String = "Provider=Microsoft.Ace.Oledb.12.0;Data Source=C:\Car\db\car.accdb;"
        Dim conn As New OleDbConnection(conStr)
        conn.Open()
        Dim sql As String = "SELECT * FROM Admin"
        Dim cmd As New OleDbCommand(sql, conn)
        Dim reader As OleDbDataReader = cmd.ExecuteReader()
        Dim TbUsername As String = TbxUsername.Text
        Dim TbPassword As String = TbxPassword.Text
        Dim _name() As String
        Dim pass() As String
        While (reader.Read())
            _name(reader.HasRows) = reader("Username")
            pass(reader.HasRows) = reader("Password")
        End While
        If (TbUsername <> "") Then
            If (TbUsername = _name(reader.HasRows)) Then
                If (TbPassword = pass(reader.HasRows)) Then
                    Dim home As New Form2()
                    home.Show()
                Else
                    MsgBox("Username หรือ Password ผิดพลาด")
                End If
            Else
                MsgBox("Username หรือ Password ผิดพลาด")
            End If
        Else
            MsgBox("กรุณาใส่ Username และ Password")
        End If

        conn.Close()

    End Sub


End Class