Slow database query: Using VB.net connecting to Access - vb.net

Question

I have a program which will only allow a certain amount of concurrent users to use the program at one time. To do this I have a single table in an access database which holds each user that is using the program. Now although this does work the query seems to be running very slowly, I am certain it is something to do with the database functions as it was running fine before I implemented them.
Here are my functions:
Public Function openDB() As Boolean
cnn.Open()
Return True
End Function
Public Function closeDB() As Boolean
cnn.Close()
Return True
End Function
Then there is the function for checking the database. This is where I think it may be tripping up because I have 2 queries running here:
Public Function CheckLicence() As Boolean
Dim result As Boolean = HandleRegistry()
If result = True Then
Dim _table As String = "Users"
Dim query As String = "SELECT * FROM " & _table & " WHERE Machine_ID='" & CpuId() & "'"
Dim sizeQuery As String = "SELECT COUNT(*) FROM " & _table
Dim NoUsers As Integer = 0
Dim ds As New DataSet
Dim dr As OleDbDataReader
Dim cmd As New OleDbCommand(query, cnn)
dr = cmd.ExecuteReader
Dim sizeCdm As New OleDbCommand(sizeQuery, cnn)
NoUsers = sizeCdm.ExecuteScalar()
If dr.Read() Then
Return True
Else
If NoUsers < My.Settings.NoUsers Then
addToDB()
Else
MsgBox("Too many users are currently using this program. Clear a user and try again.")
Return False
End If
End If
Else
MsgBox("Your licence has expired, contact support to purchase a new licence.")
Return False
End If
Return True
End Function
And to add and remove I have to get the cpu id, I found the code for that on here somewhere it does work but maybe that could be the slow part, I dont actually know if this is the correct way of getting it.
Public Sub addToDB()
Dim _table As String = "Users"
Dim query As String = "INSERT INTO " & _table & " ([User], [Machine_ID]) VALUES (?,?)"
Dim ds As New DataSet
Dim cmd As New OleDbCommand(query, cnn)
cmd.Parameters.AddWithValue("?", Environment.UserName)
cmd.Parameters.AddWithValue("?", CpuId())
cmd.ExecuteNonQuery()
End Sub
Public Sub RemoveFromDB()
Dim _table As String = "Users"
Dim query As String = "DELETE * FROM " & _table & " WHERE Machine_ID='" & CpuId() & "'"
Dim ds As New DataSet
Dim cmd As New OleDbCommand(query, cnn)
cmd.ExecuteNonQuery()
End Sub
Private Function CpuId() As String
Dim computer As String = "."
Dim wmi As Object = GetObject("winmgmts:" &
"{impersonationLevel=impersonate}!\\" &
computer & "\root\cimv2")
Dim processors As Object = wmi.ExecQuery("Select * from " &
"Win32_Processor")
Dim cpu_ids As String = ""
For Each cpu As Object In processors
cpu_ids = cpu_ids & ", " & cpu.ProcessorId
Next cpu
If cpu_ids.Length > 0 Then cpu_ids =
cpu_ids.Substring(2)
Return cpu_ids
End Function

Answer 1

How about storing the cpuID globally and fetching only once. Also, use the Using construct on anything that needs to be disposed. Lastly, run a few StopWatches around your methods to see which one is slow or just debug through each one to find the slow method.

Answer 2

Answer:
How about storing the cpuID globally and fetching only once. Also, use the Using >construct on anything that needs to be disposed. Lastly, run a few StopWatches >around your methods to see which one is slow or just debug through each one to >find the slow method. – Andrew Mortimer
Moved the call for getting the cpuID to the program initialisation so that it runs on startup. This made it run much faster than it did before.