How do I update an existing cookie with more than one value (MVC4 C#)

Can't figure out how to update the cookie without rewriting all the cookies.

How would I just update the one value?

This is what I have:

HttpCookie uInfo = Request.Cookies["userInfo"];
           
                //  == 4 other values in the uerInfo cookie
                uInfo["zoneNumber"] = Zone;     // Zone is a public var
    

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