深入解析C#中的泛型类与泛型接口

将接口指定为类型参数的约束时，只能使用实现此接口的类型。下面的代码示例显示从 SortedList<T> 类派生的 GenericList<T> 类。
 SortedList<T> 添加约束 where T : IComparable<T>。这将使 SortedList<T> 中的 BubbleSort 方法能够对列表元素使用泛型 CompareTo 方法。在此示例中，列表元素为简单类，即实现 Person 的 IComparable<Person>。

//Type parameter T in angle brackets.
public class GenericList<T> : System.Collections.Generic.IEnumerable<T>
{
  protected Node head;
  protected Node current = null;

  // Nested class is also generic on T
  protected class Node
  {
    public Node next;
    private T data; //T as private member datatype

    public Node(T t) //T used in non-generic constructor
    {
      next = null;
      data = t;
    }

    public Node Next
    {
      get { return next; }
      set { next = value; }
    }

    public T Data //T as return type of property
    {
      get { return data; }
      set { data = value; }
    }
  }

  public GenericList() //constructor
  {
    head = null;
  }

  public void AddHead(T t) //T as method parameter type
  {
    Node n = new Node(t);
    n.Next = head;
    head = n;
  }

  // Implementation of the iterator
  public System.Collections.Generic.IEnumerator<T> GetEnumerator()
  {
    Node current = head;
    while (current != null)
    {
      yield return current.Data;
      current = current.Next;
    }
  }

  // IEnumerable<T> inherits from IEnumerable, therefore this class 
  // must implement both the generic and non-generic versions of 
  // GetEnumerator. In most cases, the non-generic method can 
  // simply call the generic method.
  System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
  {
    return GetEnumerator();
  }
}

public class SortedList<T> : GenericList<T> where T : System.IComparable<T>
{
  // A simple, unoptimized sort algorithm that 
  // orders list elements from lowest to highest:

  public void BubbleSort()
  {
    if (null == head || null == head.Next)
    {
      return;
    }
    bool swapped;

    do
    {
      Node previous = null;
      Node current = head;
      swapped = false;

      while (current.next != null)
      {
        // Because we need to call this method, the SortedList
        // class is constrained on IEnumerable<T>
        if (current.Data.CompareTo(current.next.Data) > 0)
        {
          Node tmp = current.next;
          current.next = current.next.next;
          tmp.next = current;

          if (previous == null)
          {
            head = tmp;
          }
          else
          {
            previous.next = tmp;
          }
          previous = tmp;
          swapped = true;
        }
        else
        {
          previous = current;
          current = current.next;
        }
      }
    } while (swapped);
  }
}

// A simple class that implements IComparable<T> using itself as the 
// type argument. This is a common design pattern in objects that 
// are stored in generic lists.
public class Person : System.IComparable<Person>
{
  string name;
  int age;

  public Person(string s, int i)
  {
    name = s;
    age = i;
  }

  // This will cause list elements to be sorted on age values.
  public int CompareTo(Person p)
  {
    return age - p.age;
  }

  public override string ToString()
  {
    return name + ":" + age;
  }

  // Must implement Equals.
  public bool Equals(Person p)
  {
    return (this.age == p.age);
  }
}

class Program
{
  static void Main()
  {
    //Declare and instantiate a new generic SortedList class.
    //Person is the type argument.
    SortedList<Person> list = new SortedList<Person>();

    //Create name and age values to initialize Person objects.
    string[] names = new string[] 
    { 
      "Franscoise", 
      "Bill", 
      "Li", 
      "Sandra", 
      "Gunnar", 
      "Alok", 
      "Hiroyuki", 
      "Maria", 
      "Alessandro", 
      "Raul" 
    };

    int[] ages = new int[] { 45, 19, 28, 23, 18, 9, 108, 72, 30, 35 };

    //Populate the list.
    for (int x = 0; x < 10; x++)
    {
      list.AddHead(new Person(names[x], ages[x]));
    }

    //Print out unsorted list.
    foreach (Person p in list)
    {
      System.Console.WriteLine(p.ToString());
    }
    System.Console.WriteLine("Done with unsorted list");

    //Sort the list.
    list.BubbleSort();

    //Print out sorted list.
    foreach (Person p in list)
    {
      System.Console.WriteLine(p.ToString());
    }
    System.Console.WriteLine("Done with sorted list");
  }
}

								 
 3/4   首页 上一页 1 2 3 4 下一页 尾页