ช่วยตรวจสอบโค้ดให้ทีครับ มันerror ตรง DB. อ่าครับ เป็นอะไรก็ไม่รู้อ่าครับ

Option Explicit On
Option Strict On
Imports System.Data.SqlClient
Imports System.Data
Imports System.Globalization
Imports System.Text
Imports System.Drawing.Drawing2D
Imports System.IO
Imports System.Security.Cryptography
Public Class frmlogin
    Dim Conn As SqlConnection
    Dim com As SqlCommand
    Dim dr As SqlDataReader
    Dim tr As SqlTransaction

    Dim sb As StringBuilder
    Dim ms As MemoryStream
    Dim desCrypt As DESCryptoServiceProvider
    Dim cs As CryptoStream
    Dim PwdWithEncrypt As String

    Dim CurrentAuthentication As String

    Dim IsChange As Boolean = False
    Private Sub btncancel_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btncancel.Click
        Dim result As MsgBoxResult
        result = CType(MessageBox.Show("คุณต้องการออกจากระบบหรือไม่", "ออกจากระบบ", MessageBoxButtons.YesNo, MessageBoxIcon.Question), MsgBoxResult)
        If result = MsgBoxResult.Yes Then
            End
        End If
    End Sub
    Private Sub frmlogin_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim strConn As String
        strConn = DB.strConn
        Conn = New SqlConnection()
        With Conn
            If .State = ConnectionState.Open Then .Close()
            .ConnectionString = strConn
            .Open()
        End With
    End Sub

    Private Sub btnok_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnok.Click
        If (txtusername.Text.Trim() = "") OrElse (txtpassword.Text.Trim() = "") Then
            txtusername.Focus()
            Exit Sub
        End If

        Dim CurrentLogin As Boolean = False
        CurrentLogin = Login(txtusername.Text, txtpassword.Text)

        If CurrentLogin = True Then
            DB.UserName = txtusername.Text.Trim()
            DB.UserAuthentication = CurrentAuthentication
            main_manu.Show()
            Me.Hide()
        Else
            MessageBox.Show("UserName หรือ Password ที่คุณป้อน ไม่ถูกต้อง !!!", "ผลการทำงาน", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
            CurrentAuthentication = ""
            txtusername.Text = ""
            txtusername.Focus()
            txtpassword.Text = ""
        End If
    End Sub

    Private Function Login(ByVal _UserName As String, ByVal _Password As String) As Boolean
        sb = New StringBuilder()
        sb.Append("SELECT UserName,Password,Auth")
        sb.Append(" FROM UserName")
        sb.Append(" WHERE (UserName=@UserName)")
        sb.Append(" AND (Password=@Password)")
        sb.Append(" AND (IsNormal='1')")
        Dim sqlLogin As String
        sqlLogin = sb.ToString()

        Dim CurrentIV As Byte() = New Byte() {51, 52, 53, 54, 55, 56, 57, 58}
        Dim CurrentKey As Byte() = {}

        If _UserName.Length = 8 Then
            CurrentKey = Encoding.ASCII.GetBytes(_UserName)
        ElseIf _UserName.Length > 8 Then
            CurrentKey = Encoding.ASCII.GetBytes(_UserName.Substring(0, 8))
        Else
            Dim i As Integer
            Dim AddString As String = _UserName.Substring(0, 1)
            Dim TotalLoop As Integer = 8 - CInt(_UserName.Length)
            Dim tmpKey As String = _UserName

            For i = 1 To TotalLoop
                tmpKey = tmpKey & AddString
            Next

            CurrentKey = Encoding.ASCII.GetBytes(tmpKey)
        End If

        desCrypt = New DESCryptoServiceProvider
        With desCrypt
            .IV = CurrentIV
            .Key = CurrentKey
        End With

        ms = New MemoryStream
        ms.Position = 0

        cs = New CryptoStream(ms, desCrypt.CreateEncryptor, CryptoStreamMode.Write)
        Dim arrByte As Byte() = Encoding.ASCII.GetBytes(_Password)
        cs.Write(arrByte, 0, arrByte.Length)
        cs.FlushFinalBlock()
        cs.Close()

        PwdWithEncrypt = Convert.ToBase64String(ms.ToArray())

        com = New SqlCommand()
        With com
            .CommandText = sqlLogin
            .CommandType = CommandType.Text
            .Connection = Conn
            .Parameters.Clear()
            .Parameters.Add("@UserName", SqlDbType.NVarChar).Value = _UserName
            .Parameters.Add("@Password", SqlDbType.NVarChar).Value = PwdWithEncrypt
            dr = .ExecuteReader()
            If dr.HasRows Then
                With dr
                    .Read()
                    CurrentAuthentication = .GetString(.GetOrdinal("Auth"))
                End With
                dr.Close()
                Return True
            Else
                dr.Close()
                Return False
            End If
        End With
    End Function
   
End Class