改善C#編程的50個建議(31-35)

-------------------------翻譯 By Cryking-----------------------------
-----------------------轉載請注明出處,謝謝!------------------------

題外話:關於C#_Effective(Covers C#4.0)一書的翻譯也快已完結,由於水平有限,錯誤在所難免,尤其很多地方有所省略(一來英文水平有限,木辦法;二來自己感覺原作者有時太啰嗦了)或加上了自己的一些見解,所以還請各位自己明辨。

PS:由於一些無德網站惡意轉載本博客文章(連轉字都不帶一個的),所以加上了上面的鏈接文字,防君子不防小人,還請尊重鄙人的勞動成果,感謝!

31 使用IComparable和IComparer實現順序關系
你的類型需要順序關系來描述集合元素怎麼排序和查詢。.NET框架定義了IComparable和IComparer兩種接口來描述這種順序關系。你可以定義你自己的關系操作實現(>,<,<=,>=)來提供指定類型的比較。
IComparable接口包含了一個方法:CompareTo(),IComparable用在.NET的最新的API中,而舊的API使用IComparable接口.因此為了保持兼容性,當你實現IComparable時,你也應該實現IComparable.IComparable帶有System.Object類型的參數:

  public struct Customer : IComparable, IComparable
    {
        private readonly string name;
        public Customer(string name)
        {
            this.name = name;
        }
        #region IComparable Members
        public int CompareTo(Customer other)
        {
            return name.CompareTo(other.name);
        }
        #endregion
        #region IComparable Members
        int IComparable.CompareTo(object obj)
        {
            if (!(obj is Customer))
                throw new ArgumentException("Argument is not a Customer", "obj");
            Customer otherCustomer = (Customer)obj;
            return this.CompareTo(otherCustomer);
        }
        #endregion
    }

    // Relational Operators.
    public static bool operator <(Customer left,
    Customer right)
    {
        return left.CompareTo(right) < 0;
    }
    public static bool operator <=(Customer left,
    Customer right)
    {
        return left.CompareTo(right) <= 0;
    }
    public static bool operator >(Customer left,
    Customer right)
    {
        return left.CompareTo(right) > 0;
    }
    public static bool operator >=(Customer left,Customer right)
    {
        return left.CompareTo(right) >= 0;
    }

    class BaseType : ICloneable
    {
        private string label = "class name";
        private int[] values = new int[10];
        public object Clone()
        {
            BaseType rVal = new BaseType();
            rVal.label = label;
            for (int i = 0; i < values.Length; i++)
                rVal.values[i] = values[i];
            return rVal;
        }
    }
    class Derived : BaseType
    {
        private double[] dValues = new double[10];
        static void Main(string[] args)
        {
            Derived d = new Derived();
            Derived d2 = d.Clone() as Derived;
            if (d2 == null)
                Console.WriteLine("null");
        }
    }

class BaseType
    {
        private string label;
        private int[] values;
        protected BaseType()
        {
            label = "class name";
            values = new int[10];
        }
        // Used by devived values to clone
        protected BaseType(BaseType right)
        {
            label = right.label;
            values = right.values.Clone() as int[];
        }
    }
    sealed class Derived : BaseType, ICloneable
    {
        private double[] dValues = new double[10];
        public Derived()
        {
            dValues = new double[10];
        }
        // Construct a copy
        // using the base class copy ctor
        private Derived(Derived right) :base(right)
        {
            dValues = right.dValues.Clone()
            as double[];
        }
        public object Clone()
        {
            Derived rVal = new Derived(this);
            return rVal;
        }
    }

    public class MyClass
    {
        public void MagicMethod()
        {
            // details elided.
        }
    }
    public class MyOtherClass : MyClass
    {
        // Redefine MagicMethod for this class.
        public new void MagicMethod()
        {
            // details elided
        }
    }

public class MyWidget : BaseWidget
{
  public void new NormalizeValues()
 {
    // details elided.
    // Call the base class only if (by luck)
    // the new method does the same operation.
    base.NormalizeValues();
 }
}