Single user and multiple user license

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C#

I am working on single and multiple user license if user install application in his system, only allow one user access one server license user cannot install multiple system ? if user download application from website format page of website is under below.

Order Page

Just suppose

$100.99 $200.99 #500

One system license Two system license Unlimited

download detail

Order Now Order Now Order Now

but logic required for desktop application C#

What I have tried:

I have applied this

private string GetMacAddress()
{
string macAddresses = string.Empty;

foreach (NetworkInterface nic in NetworkInterface.GetAllNetworkInterfaces())
{
if (nic.OperationalStatus == OperationalStatus.Up)
{
macAddresses += nic.GetPhysicalAddress().ToString();
break;
}
}

return macAddresses;
}