[C#.Net&Linq]LINQ to Object 学习笔记(资料群组GroupBy、ToLookup、ToDictionary)

  1:  //===GroupBy===

   2:  //IEnumerable<IGrouping<TKey,TElement>>列举型别

   3:  IEnumerable<IGrouping<string,Authors>> contacts = from author in Authors

   4:    group author by author.State;

   5:  //GroupBy转换后，存储在IGrouping

   6:  //IGrouping<TKey,TElement>

   7:  foreach(IGrouping<string,Authors> item in contacts)

   8:  {

   9:      Console.WriteLine(item.Key);

  10:      Console.WriteLine(item);

  11:  }

  12:  //使用匿名型別

  13:  var contact = Authors.GroupBy(author=>author.State);

  14:  foreach(var item in contact)

  15:  {

  16:      Console.WriteLine(item.Key);

  17:      Console.WriteLine(item);

  18:  }

  19:   

  20:   

  21:  //===ToLookup===

  22:  //集合物件Authors的ToLookup方法，产生泛型版本的ILookup

  23:  ILookup<string,Authors> contacts = Authors.ToLookup(author=>author.State);

  24:  //与GroupBy一样ToLookup转换后，存储在IGrouping

  25:  //IGrouping<TKey,TElement>

  26:  foreach(IGrouping<string,Authors> items in contacts)

  27:  {

  28:    Console.WriteLine(items.Key);

  29:    Console.WriteLine(items);

  30:  }

  31:  //使用匿名型別

  32:  var contact = Authors.ToLookup(author=>author.State);

  33:  foreach(var items in contact)

  34:  {

  35:    Console.WriteLine(items.Key);

  36:    Console.WriteLine(items);

  37:  }

   1: //===ToDictionary===
   2:  Dictionary<string, Authors> contacts = Authors.ToDictionary(author=>author.Au_id);
   3:  foreach(KeyValuePair<string, Authors> item in contacts)
   4:  {
   5:     Console.WriteLine(item.Key);
   6:     Console.WriteLine(item.Value);
   7:  }
   8:  //使用匿名型別
   9:  var contacts = Authors.ToDictionary(author=>author.Au_id);
  10:  foreach(var item in contacts)
  11:  {
  12:     Console.WriteLine(item.Key);
  13:     Console.WriteLine(item.Value);
  14:  }