How to get subnet mask using .net?

Question

I want to get client subnet mask using c#.

How can I get it?

Answer 1

First of all, check NetworkInterface class first. There are a lot of information in it. And these articles will be helpful for you:

• IP Address Calculations with C# (Subnetmasks, Networks, …)
• Get Subnet Mask
• Finding subnet mask from IP4 address using c#

Answer 2

It's impossible to know what subnet mask client's network is using (if we are talking about D and E class IP addresses).

My assumption is that by "client" you mean a remote computer connected to your server. Otherwise see @Soner Gönül answer.