if (user?.Identity?.IsAuthenticated ?? false)这几个问号分别都代表啥意思？

悬赏园豆：5 [已解决问题] 浏览: 229次解决于 2018-05-16 13:27

            var user = HttpContext.User;
            if (user?.Identity?.IsAuthenticated ?? false)
            {

            }
            else
            {

            }

如题，求解。

屌丝大叔的笔记 | 初学一级 | 园豆：67
提问于：2018-05-16 10:26

牛逼的写法，谢谢dudu，xiexie演员。

– 屌丝大叔的笔记 1年前回复

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最佳答案

? 如果不为null，执行其后的方法；?? 如果为null，返回其后的值。

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其他回答(1)

等价于

         bool isNull;
            if (user != null)
            {
                if (user.Identity != null)
                {
                    if (user.Identity.IsAuthenticated != null)
                    {
                        isNull = user.Identity.IsAuthenticated;
                    }
                }
            }
            isNull = false;
            if (isNull)
            {
        } </span></pre>

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回复 | 写代码的相声演员 | 园豆：541 (小虾三级) | 2018-05-16 11:38

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if (user?.Identity?.IsAuthenticated ?? false)这几个问号分别都代表啥意思？

if (user?.Identity?.IsAuthenticated ?? false)这几个问号分别都代表啥意思？

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