Linq To List 集合查詢

     //Linq對集合的各種查詢
      public static void Run()
      {
          List<Customers> customerlist = new List<Customers>();
          customerlist.Add(new Customers() { id = 1, Name = "Jack", Custom = "Mis" });
          customerlist.Add(new Customers() { id = 2, Name = "Lus", Custom = "Google" });
          customerlist.Add(new Customers() { id = 3, Name = "Qiao", Custom = "Baidu" });
          customerlist.Add(new Customers() { id = 4, Name = "Qiao", Custom = "Apple" });
          customerlist.Add(new Customers() { id = 5, Name = "Adb", Custom = "Adobe" });
 
          //簡單的查詢
          var customerQuery = from query in customerlist
                              select query;
 
          //帶where篩選
          var customerWhereQuery = from query in customerlist
                                   where query.id == 1 && query.Name == "Lus"
                                   select query;
 
          //排序Ordering
          var customerOrderingQuery = from query in customerlist
                                      where query.Name == "Lus"
                                      orderby query.id ascending
                                      select query;
 
          //分組Group by
          var customerGroupbyQuery = from query in customerlist
                                     group query by query.Name;
          //可以使用into進一步查詢
          var customerGroupbyIntoQuery = from query in customerlist
                                         group query by query.Name into queryGroup
                                         where queryGroup.Key == "Qiao"
                                         select queryGroup;
          //聯接查詢 join 子句始終針對對象集合而非直接針對數據庫表運行。
          List<Customers> customerJoinlist = new List<Customers>();
          customerJoinlist.Add(new Customers() { id = 1, Name = "Jack", Custom = "Mis" });
          customerJoinlist.Add(new Customers() { id = 2, Name = "Lus", Custom = "Google" });
          customerJoinlist.Add(new Customers() { id = 3, Name = "Qiao", Custom = "Baidu" });
          var customerJoinQuery = from query1 in customerlist
                                  join query2 in customerJoinlist
                                  on query1.id equals query2.id
                                  select new { CustomerName = query1.Name, CustomerName2 = query2.Name };
 
          //數據源的類型參數始終爲查詢中的範圍變量的類型。
          //比如List<Customers> 類型爲Customers 在循環迭代的時候類型必須可以隱式轉換爲Customer 有一種情況是
          //這種情況下Customers類型轉換爲了String ..在select query.Name已經將查詢目標類型定位了String類型
          var customerTypeQuery = from query in customerlist
                                  where query.Name == "Lus"
                                  select query.Name;
 
          //結合Lamdba對List集合篩選(s => s.Name == "Qiao")
          List<Customers> listString = customerlist.Where(s => s.Name == "Qiao").ToList();
 
 
      }
  }
 
  public class Customers
  {
      public int id { get; set; }
 
      public string Name { get; set; }
 
      public string Custom { get; set; }
  }