这种写法啥意思啊

[橙色阳光]

 var user = Global.userIpList.FirstOrDefault(u => u.UserId == CookieInfo.UserId.ToInt());

括号里的 u => u.UserId == CookieInfo.UserId.ToInt()

[巴士上的邂逅]

lambda表达式，匿名方法。 可用下边代码替换

private bool Method(User u)
{
    return .UserId == CookieInfo.UserId.ToInt();
}
...
 var user = Global.userIpList.FirstOrDefault(Method);

[正怒月神]

var user = Global.userIpList.FirstOrDefault(u => u.UserId == CookieInfo.UserId.ToInt());

等于 select * from userIpList where UserID=CookieInfo.UserId 这是lambda，匿名表达式