SelectManyで要素の中の要素を検索するサンプル

SelectManySample.cs

	class Group {
		public decimal No { get; set; }
		public string Name { get; set; }
		public List<Member> Members { get; set; }
	}

	class Member {
		public decimal No { get; set; }
		public string Name { get; set; }
		public decimal Age { get; set; }
		public bool IsIndoor { get; set; }
	}

	class SelectManySample {
		static void Main(string[] args) {

			// 初期化：GroupクラスはMemberクラスのリストを要素に持つ
			Group[] group =
			{ new Group { No = 1, Name = "Cat", Members = new List<Member> {
					new Member { No = 1, Name = "Tama", Age = 12, IsIndoor = true },
					new Member { No = 2, Name = "Mike", Age = 9, IsIndoor = true },
					new Member { No = 3, Name = "Chibi", Age = 1, IsIndoor = true },
					new Member { No = 4, Name = "Mosa", Age = 3, IsIndoor = false },
					new Member { No = 5, Name = "Grow", Age = 5, IsIndoor = false },
				}},
				new Group { No = 2, Name = "Dog", Members = new List<Member> {
					new Member { No = 1, Name = "Taro", Age = 5, IsIndoor = false },
					new Member { No = 2, Name = "Shiro", Age = 10, IsIndoor = true },
					new Member { No = 2, Name = "Kuma", Age = 7, IsIndoor = false },
				}},
				new Group { No = 3, Name = "Turtle", Members = new List<Member> {
					new Member { No = 1, Name = "Kamenashi", Age = 80, IsIndoor = true },
					new Member { No = 2, Name = "Kameyama", Age = 55, IsIndoor = true },
				}},
			};

			// IsIndoor == true の Group Name と Member Name を取得
			var q = group
				.SelectMany(r => r.Members, (g, m) => new { g, m })
				.Where(r => r.m.IsIndoor == true)
				.Select(r => new { GroupName = r.g.Name, MemberName = r.m.Name });

			// 表示
			foreach (var v in q) {
				Console.WriteLine(string.Format("[{0}] {1}", v.GroupName, v.MemberName));
			}
		}
	}