Koneksi database pada Visual Studio 2010

Imports System.Drawing.Bitmap
Imports System.Drawing.Image
Imports Microsoft.VisualBasic
Imports System.Data.Sql

Public Class classkoneksi
    Protected SQL As String
    Protected Cn As SqlClient.SqlConnection
    Protected Cmd As SqlClient.SqlCommand
    Protected Da As SqlClient.SqlDataAdapter
    Protected Ds As DataSet
    Protected Dt As DataTable

    Public Function OpenConn() As Boolean
        Cn = New SqlClient.SqlConnection("Data Source=USER-PC\KOM-1;Initial Catalog=penjualan20; Persist Security Info = true; password = "")
        Cn.Open()
        If Cn.State <> ConnectionState.Open Then
            Return False
        Else
            Return True
        End If
    End Function
    Public Sub CloseConn()
        If Not IsNothing(Cn) Then
            Cn.Close()
            Cn = Nothing
        End If
    End Sub

    Public Function ExecuteQuery(ByVal Query As String) As DataTable
        If Not OpenConn() Then
            MsgBox("Koneksi Gagal..!!", MsgBoxStyle.Critical, "Access Failed")
            Return Nothing
            Exit Function
        End If
        Cmd = New SqlClient.SqlCommand(Query, Cn)
        Da = New SqlClient.SqlDataAdapter
        Da.SelectCommand = Cmd
        Ds = New Data.DataSet
        Da.Fill(Ds)
        Dt = Ds.Tables(0)
        Return Dt
        Dt = Nothing
        Ds = Nothing
        Da = Nothing
        Cmd = Nothing
        CloseConn()
    End Function
    Public Sub ExecuteNonQuery(ByVal Query As String)
        If Not OpenConn() Then
            MsgBox("Koneksi Gagal..!!", MsgBoxStyle.Critical, "Access Failed..!!")
            Exit Sub
        End If
        Cmd = New SqlClient.SqlCommand
        Cmd.Connection = Cn
        Cmd.CommandType = CommandType.Text
        Cmd.CommandText = Query
        Cmd.ExecuteNonQuery()
        Cmd = Nothing
        CloseConn()
    End Sub
End Class

Public Module modul
    Public gl_user_login As String
    Public gl_level_login As String

    Public gl_kode_supplier As String

    Public gl_nama_supplier As String
    Public gl_alamat_supplier As String
    Public gl_telepon_supplier As String

    Public gl_kode_Barang As String
    Public gl_nama_Barang As String
    Public gl_ukuran_Barang As String
    Public gl_merk_Barang As String
    Public gl_harga_Barang As String
    Public gl_stok_Barang As String

    Public gl_kode_customer As String
    Public gl_nama_customer As String
    Public gl_alamat_customer As String
    Public gl_tetepon_customer As String
    Public gl_status_customer As String

    Public gl_filter_kode_customer As String
End Module