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[ASP.net教程]对集合排序的三种方式


对集合排序,可能最先想到的是使用OrderBy方法。

 

  class Program
  {
    static void Main(string[] args)
    {
      IEnumerable<Student> result = GetStudents().OrderBy(r => r.Score);
      foreach (var item in result)
      {
        Console.WriteLine(item.Name + "--" + item.Score);
      }
      Console.ReadKey();
    }
    private static List<Student> GetStudents()
    {
      return new List<Student>()
      {
        new Student(){Id = 1, Name = "张三",Age = 15, Score = 80},
        new Student(){Id = 2, Name = "李四",Age = 16, Score = 70},
        new Student(){Id = 3, Name = "赵武",Age = 14, Score = 90}
      };
    }
  }
  public class Student 
  {
    public int Id { get; set; }
    public string Name { get; set; }
    public int Age { get; set; }
    public int Score { get; set; }
  }

 

以上,OrderBy返回的类型是IEnumerable<Student>。

 

如果想使用List<T>的Sort方法,就需要让Student实现IComparable<Student>接口。

 

  class Program
  {
    static void Main(string[] args)
    {
      List<Student> result = GetStudents();
      result.Sort();
      foreach (var item in result)
      {
        Console.WriteLine(item.Name + "--" + item.Score);
      }
      Console.ReadKey();
    }
    private static List<Student> GetStudents()
    {
      return new List<Student>()
      {
        new Student(){Id = 1, Name = "张三",Age = 15, Score = 80},
        new Student(){Id = 2, Name = "李四",Age = 16, Score = 70},
        new Student(){Id = 3, Name = "赵武",Age = 14, Score = 90}
      };
    }
  }
  public class Student : IComparable<Student>
  {
    public int Id { get; set; }
    public string Name { get; set; }
    public int Age { get; set; }
    public int Score { get; set; }
    
    public int CompareTo(Student other)
    {
     return this.Score.CompareTo(other.Score);
    }
  }

 

让Student实现IComparable<Student>接口固然很好,如果Student是一个密封类,我们无法让其实现IComparable<Student>接口呢?不用担心,Sort方法提供了一个重载,可以接收IComparer接口类型。

 

  class Program
  {
    static void Main(string[] args)
    {
      List<Student> result = GetStudents();
      result.Sort(new StudentSorter());
      foreach (var item in result)
      {
        Console.WriteLine(item.Name + "--" + item.Score);
      }
      Console.ReadKey();
    }
    private static List<Student> GetStudents()
    {
      return new List<Student>()
      {
        new Student(){Id = 1, Name = "张三",Age = 15, Score = 80},
        new Student(){Id = 2, Name = "李四",Age = 16, Score = 70},
        new Student(){Id = 3, Name = "赵武",Age = 14, Score = 90}
      };
    }
  }
  public class Student
  {
    public int Id { get; set; }
    public string Name { get; set; }
    public int Age { get; set; }
    public int Score { get; set; }
  }
  public class StudentSorter : IComparer<Student>
  {
    public int Compare(Student x, Student y)
    {
      return x.Score.CompareTo(y.Score);
    }
  }

 

综上,如果我们想对一个集合排序,大致有三种方式:

 

1、使用SortBy方法,返回IEnumerable<T>类型。
2、让集合元素实现IComparable<T>接口,再使用Sort方法,返回void。
3、集合元素不实现IComparable<T>接口,针对集合元素类型写一个实现IComparer<T>接口的类,把该类实例作为Sort方法的参数。