Question

from t in Tasks
join user in UserInfo on t.Publisher equals user.Account into temp
from userinfo in temp.DefaultIfEmpty()
select new
{
    t.Title,
    IsCertificated = userinfo.IsCertificated
}

有些代码喜欢。 IsCertificated是布尔类型，当userinfo为null时，此查询将不起作用。

不为System.Boolean
指定Null值类型

我知道它可以修改：

 select new
    {
        t.Title,
        IsCertificated =userinfo == null?false: userinfo.IsCertificated
    }

但是，我的userinfo有太多非空属性。我如何处置它？

Answer 1

您可以将条件运算符拉出对象创建。

from t in Tasks
join user in UserInfo on t.Publisher equals user.Account into temp
from userinfo in temp.DefaultIfEmpty()
select userinfo != null
    ? new
        {
            t.Title,
            IsCertificated = userinfo.IsCertificated
        }
    : new
        {
            t.Title,
            IsCertificated = false
        }

LINQ使用可空值继续加入

1 个答案: