Screenshot automatically using csharp

i have one page in asp.net. in that below url are there. using click of button i want to capture screen shot of all below url and save it into one folder

Page design as follows (URL as follows)

www.google.com

https://www.onlinesbi.com/

https://www.hdfcbank.com

i have one button called Caputre screenshot. when i click capture screen shot i want to capture screen shot of all the above  URL and save itin to one folder 

how to do using asp.net C#