Retrieve user data from gmail and yahoo login

Question

Hello,

Good Evening,

In want to retrieve user data to SignIn through Gmail or Yahoo id.

I am designing such a web application in which it has no own user registration.

User can use there existing Gmail or Yahoo id to SignIn in the web application.

I want C# code for that. I have application to retrieve contact list from these Gmail and yahoo id. but it is not retrieving logged  in user information.

With Warm Regards,

Deepak Pandey