Vb. NET implementation to verify credit card number _vb.net

Vb. NET code verifies that the credit card number is correct, this code uses the Luhn algorithm to verify

Dim Creditcardnumber as String
creditcardnumber = "1234567891234563" Please enter the number you want to verify by yourself
If Creditcardnumber.length < Then
  Page.ClientScript.RegisterStartupScript (Me.GetType (), "DD", "alert (' Error number only "& Creditcardnumber.length & Password"; ", True)
Else
  Dim Int
  as Integer Dim x, num, Sun as integer
  
   for x = 0
    to num = creditcardnumber.substring (x, 1)
    If (x + 1) Mod 2 <> 0 Then ' Even multiply 1 odd number by 2
      Int (x) = n UM * 2
    Else
      Int (x) = num End
    If
  Next for
  x = 0 to
    (int (x) > 9) Then
      Int (x) = ( int (x) Mod + 1 End
    If
    sun + = Int (x)
  Next
  If (Sun Mod = 0) Then
    Page.ClientScript.RegisterS Tartupscript (Me.GetType (), "ddd", "alert (' correct credit card ');", True)
  Else
    Page.ClientScript.RegisterStartupScript (Me.GetType (), "DD", "alert (' Error);", True) end
  if


  

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