◆LINQで複合キーを使った集計処理

複合キーを匿名データ型で指定する以外は通常のグループ集計処理と同じ。
この様な処理ではあまりLINQのメリットは感じられない。（SQLで書いたほうが分かりやすく簡単かも）

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1. //複合キーでのグループ化処理  
2. public void linqGroupComplex(Form1 form)  
3. {  
4.     using (NorthWindDataContext nwnd = new NorthWindDataContext())  
5.     {  
6.         nwnd.Log = Console.Out;  
7.         var customers = nwnd.Customers.GroupBy(c => new {c.Country,c.City})  
8.                                       .OrderBy(g => g.Key.Country)  
9.                                       .ThenBy(g => g.Key.City)  
10.                                       .Select(g => new  
11.                                       {  
12.                                           g.Key.Country,  
13.                                           g.Key.City,  
14.                                           count = g.Count()  
15.                                       });  
16.         form.dataGridView1.DataSource = customers;  
17.     }  
18. }  

        //複合キーでのグループ化処理
        public void linqGroupComplex(Form1 form)
        {
            using (NorthWindDataContext nwnd = new NorthWindDataContext())
            {
                nwnd.Log = Console.Out;
                var customers = nwnd.Customers.GroupBy(c => new {c.Country,c.City})
                                              .OrderBy(g => g.Key.Country)
                                              .ThenBy(g => g.Key.City)
                                              .Select(g => new
                                              {
                                                  g.Key.Country,
                                                  g.Key.City,
                                                  count = g.Count()
                                              });
                form.dataGridView1.DataSource = customers;
            }
        }

埋め込みクエリー方式では以下のとおり。

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1. //複合キーでのグループ化処理  
2. public void linqGroupComplex(Form1 form)  
3. {  
4.     using (NorthWindDataContext nwnd = new NorthWindDataContext())  
5.     {  
6.         var customers = from c in nwnd.Customers  
7.                         group c by new{c.Country,c.City} into g  
8.                         orderby g.Key.Country,g.Key.City  
9.                         select new  
10.                         {  
11.                             g.Key.Country,  
12.                             g.Key.City,  
13.                             count = g.Count()  
14.                         };  
15.         form.dataGridView1.DataSource = customers;  
16.         Console.Beep();  
17.     }  
18. }  

        //複合キーでのグループ化処理
        public void linqGroupComplex(Form1 form)
        {
            using (NorthWindDataContext nwnd = new NorthWindDataContext())
            {
                var customers = from c in nwnd.Customers
                                group c by new{c.Country,c.City} into g
                                orderby g.Key.Country,g.Key.City
                                select new
                                {
                                    g.Key.Country,
                                    g.Key.City,
                                    count = g.Count()
                                };
                form.dataGridView1.DataSource = customers;
                Console.Beep();
            }
        }