c# - 林克 : doing a Where() clause on a nested model

Question

这可能看起来很复杂，但我实际上只是想从 A 中选择所有记录及其子项，其中子项存在某些条件。寻找我可以添加到 A 变量的语法，它允许我过滤一堆条件(比如规范模式？)

如果你有这样的嵌套 View :

var a = from Arow in Atable
        where ???
        select new AViewModel {                    // (image Products)
            id = Arow.id,
            name = Arow.Name,
            Brows = (from Brow in Arow.Brows
                     select new BViewModel {       // (sold in different regions)
                         id = Brow.id,
                         name = Brow.Name,
                         Crows = (from Crow in Brow.Crows
                                  select new CViewModel { // (and in many stores)
                                      id = Crow.id,
                                      name = Crow.Name
                                  }
                     }
        };

以及表示来自这样的网页的查询的文本(规范模式？)我们为运算符使用了 JQuery 选择器(比如 ^= 表示“开始于”)

filter[] = { "Brow.Name = Joe", "Crow.Name = Kim" }

您如何使用这些条件过滤表达式 A？换句话说，你能不能有一个像 a.Where() 这样可以过滤嵌套属性的 where 表达式？

我糟糕的尝试:

var b = from row in a
        where a.Brow.Where(b => b.name == "Joe") &&
              a.Brow.Crow.Where(c => c.name == "Kim")
        select row;

我真正需要的是这样的:

Select * 
from A join B on A.key = B.key join C on B.key = C.key -- propagated keys
where exists (select null from B where A.key = B.key and B.Name = "Joe") and
      exists (select null from C where A.key = C.key and C.Name = "Kim")

特别是如果我能做到这一点:

var result = a.Where(first).Where(second);

Answer 1

您的“糟糕尝试”离我们不远了。只需将 Any() 替换为 Where():

var b = from row in a
        where a.Brow.Any(b => b.name == "Joe") &&
              a.Brow.Crow.Any(c => c.name == "Kim")
        select row;

编辑添加:

不过，您可能想要进行不区分大小写的比较，例如 .Any(b => b.name.Equals("Joe", StringComparison.CurrentCultureIgnoreCase))。