今天在msdn里看到关于cookies的方面：

如何：删除 Cookie

if (Request.Cookies["UserSettings"] != null)
{
HttpCookie myCookie = new HttpCookie("UserSettings");
myCookie.Expires = DateTime.Now.AddDays(-1d);
Response.Cookies.Add(myCookie);
}

我根据里面写了删除 Cookie ，结果不可以。

if (Request.Cookies["UserSettings"] != null)
{
HttpCookie myCookie = Request.Cookies["UserSettings"] ;
myCookie.Expires = DateTime.Now.AddDays(-1d);
Response.Cookies.Add(myCookie);
}
这样就可以

if (Request.Cookies["UserSettings"] != null)
{
Request.Cookies["UserSettings"] = null;
}
你这么写试试