がんふぃーるど室長の不定期ブログ

(TAccumulate, TSource) => 処理

var family = new []{
    new { Name = "父", Age = 40, Sex = "男" },
    new { Name = "母", Age = 40, Sex = "女" },
    new { Name = "娘", Age = 10, Sex = "女" },
    new { Name = "爺ちゃん", Age = 70, Sex = "男" },
    new { Name = "曾婆ちゃん", Age = 100, Sex = "女" },
    new { Name = "曾曾婆ちゃん", Age = 125, Sex = "女" }
};

string startVal = string.Empty;
var AggNamePerSex = from f in family
                    group f by f.Sex into g
                    select new {
                        Sex = g.Key,
                        AggName = g.Aggregate(
                            startVal // 初期値
                            , (running, next) => running += next.Name + "," // 集計処理
                            , result => result == string.Empty ? result : result.Substring(0, result.Length -1) // 終了処理
                        )
                    };

foreach (var sexGroup in AggNamePerSex)
{
    Console.WriteLine(sexGroup.Sex + " : " + sexGroup.AggName);
}

男 : 父,爺ちゃん
女 : 母,娘,曾婆ちゃん,曾曾婆ちゃん