Develop C# code just like Captive Portal

I wanted to develop small C# application just like capative portal. Explanation : [login to view URL] will connect to any wifi avalibale eg: assume that you have wifi router(TP-Link,NetGear) at your home [login to view URL] you connect to router you will not be asked for password instead one web page will appear which will ask you from user name and password.(Just like on at airport / Hotels etc) [login to view URL] user enter username & password (this can be either OTP validation) then he can get internet access on successfully login. Reference : [login to view URL] Only genuiue developer