Question

是否可以在asp.net中使用linq中的条件运算符？我尝试过这段代码，但它显示：

   The name BusinessInstance and LocalityMaster1 is not in a scope on the left hand side of 'equal' Consider swaping the expression on either side of 'equals'.

我需要将结果作为BusinessName，（LocalityName / BusinessAddress），CityName。我的sql如下：

from BusinessInstanceInfoKeys in db.utblYPBusinessInstanceInfoKeys.Where(x=> x.BusinessName.Contains(term))
join CityMaster in db.utblCityMasters
on BusinessInstanceInfoKeys.CityID equals CityMaster.CityID

let Address = BusinessInstanceInfoKeys.LocalityID != null
              ? from LocalityMaster1 in db.utblLocalityMasters
                join BusinessInstance in db.utblYPBusinessInstanceInfoKeys
                  on BusinessInstance.LocalityID equals LocalityMaster1.LocalityID
                select new 
                {
                    LocalityMaster1.LocalityName 
                }
              : BusinessInstanceInfoKeys.BusinessAddress
select new
{
    LocalityName = BusinessInstanceInfoKeys.BusinessName + ",(" + Address + ")" + "," + CityMaster.CityName
};

有人能提出正确的建议吗？

Answer 1

要消除错误，请将其替换为：

on BusinessInstance.LocalityID equals LocalityMaster1.LocalityID

用这个：

on LocalityMaster1.LocalityID equals BusinessInstance.LocalityID

此外，您可以在let内包含三元表达式，但可能会出现几个问题：

如果您直接查询数据库（即实体框架），我不知道它能够从三元表达式生成有意义的SQL，因此它可能会抛出异常。
三元表达式中的两个条件都必须返回相同的数据类型。你的似乎没有。

根据您的评论，如果运行以下查询至少会返回一条记录，您可以尝试这样做。 （我假设 LocalityName 和 BusinessAddress 都是字符串。）

let Address = BusinessInstanceInfoKeys.LocalityID != null
              ? (from LocalityMaster1 in db.utblLocalityMasters
                 join BusinessInstance in db.utblYPBusinessInstanceInfoKeys
                   on BusinessInstance.LocalityID equals LocalityMaster1.LocalityID
                 select LocalityMaster1.LocalityName).FirstOrDefault()
              : BusinessInstanceInfoKeys.BusinessAddress

linq sql中的条件运算符

1 个答案: