LINQ - 包含在？

Question

我想在一个集合（继承另一个集合）中搜索属性值。

private ObservableCollection<User> userCollection = someData; 

public class User 
{ 
    public string Username { get; set; } 
    public ObservableCollection<Department> Memberships { get; set; } 
} 

public class Department 
{ 
    public string Name { get; set; } 
} 

//I can't use "Contains", because it requires an object of type "Department", but I don't have the object, just the string "Name" (in this case "MyDepartment") 
var result = from usr in userCollection where (usr.Memberships.Contains("MyDepartment")) select usr; 

您有什么建议吗？

Answer 1

使用IEnumerable.Any来实现你想要的。

例如：

(from usr in userCollection select usr). 
       Any(x=>x.Username.Contains("MyDepartment")) 

Answer 2

你可以使用上IEnumerable.Any()才达到你想要什么。如果集合中有一个或多个元素（谓词返回true），这将返回true。

var result = from usr in userCollection 
      where usr.Memberships.Any(m => m.Name == "MyDepartment") 
      select usr; 

Answer 3

使用你的代码示例 - 你需要选择你正在检查的部门的等效部分到一个新的集合中，然后运行Contains。

var result = from usr in userCollection where (usr.Memberships.Select(m=>m.Name).Contains("MyDepartment")) select usr; 

或者 - IEnumerable.Any是一个更好的构建在这里比Contains - 看其他答案