Many to Many Table Controller Create

Question

I have a project for school to make an auction website.

I made it in ASP.NET MVC  database first (with edmx things) 

So i have in my project 3 tables + some others:

• Auctions
• Users
• Users_Offers with : IdUsersOffers, AmountBid, DateBid, IdUser, IdAuction

  

 

That's the auction Page .

 

How can i write the controller for User_Offers  to add bid  for the current auction but to have DateBid = Datetime.Now; , IdAuction = current auction ; IdUser = User.identity.getuserid() when i pressed the "Bid Now", and only to write the amount that i want to bid in the input shown there?

 

I don't mind if when I press the "Bid Now" to redirect me to another page like this:

 

 

But i want the informations from the previous page (IdAuction) to be saved

 

I tried to make it automatically with entity framework but the result was giving me a list with all auctions and all users and I want only the current auction and current user authenticated.