Dim creditCardNumber As String
creditCardNumber = "1234567891234563" '这里请自行输入你要验证的号码
If creditCardNumber.Length < 16 Then
  Page.ClientScript.RegisterStartupScript(Me.GetType(), "dd", "alert('错误数字只有" & creditCardNumber.Length & "碼');", True)
Else
  Dim Int(15) As Integer
  Dim x, num, sun As Integer
  For x = 0 To 15
    num = creditCardNumber.Substring(x, 1)
    If (x + 1) Mod 2 <> 0 Then '偶数乘1奇数乘2
      Int(x) = num * 2
    Else
      Int(x) = num
    End If
  Next
  For x = 0 To 15
    If (Int(x) > 9) Then
      Int(x) = (Int(x) Mod 10) + 1
    End If
    sun += Int(x)
  Next
  If (sun Mod 10 = 0) Then
    Page.ClientScript.RegisterStartupScript(Me.GetType(), "ddd", "alert('正确的信用卡');", True)
  Else
    Page.ClientScript.RegisterStartupScript(Me.GetType(), "dd", "alert('错误);", True)
  End If
End If