I think it is not possible to log in websites such as Yahoo with request.credentials, and to use CookieContainer I think I should log in at least one time that the cookie can be stored.

I logged in with IE and visual studio's browser and it made the cookie, because after that login, the website logs me in automatically. But when I go to the page within my program it doesn't seem to be logged in, I mean probably when I request the address through my program it doesn't use the cookie which is stored by IE or visual studio's browser.

So now I want to log in the site through my program. To do this I should write my username and password in two text boxes in the log in page, But I don't know how to do this. I've searched a lot about posting data in a webpage but I couldn't find anything. I want some help please!