ICompare与Sort

今天参与了一个讨论关于对Dictionary排序问题：

http://community.youkuaiyun.com/Expert/topic/5682/5682646.xml?temp=2.558535E-02 

小结如下：

• .net framework2.0 可以使用范型对简单数据类型进行比较排序，例如：

                  // GetUniqueRandom可以获得一组随机数 返回List<int>
                List < int >  uRand  =  GetUniqueRandom();  
                uRand.Sort();
                Enumerator objEnumT  =  ((IEnumerable)uRand).GetEnumerator();
                 int  i  =   0 ;
                 while  (objEnumT.MoveNext())
                 ... {
                      Object obj = objEnumT.Current;
                      Console.WriteLine(" [{0}]: {1}", (Int32)i++, (int)obj);
                }

 

• .net framework 1.1不支持反省范型，可以将hashtable中的数字输出到arraylist中然后排序，但要重写ICompare接口。先给出一个例子：

 

                Hashtable ht  =   new  Hashtable();
                 int  index  =   0 ;
                 int [] uRand  =  GetUniqueRandom();
                 foreach ( int  rand  in  uRand)
                 ... {
                    index ++ ;
                    ht.Add(index, rand);
                }

                ArrayList al  =   new  ArrayList(ht);
                IComparer myComparer  =   new  myComparerClass();
                al.Sort(myComparer);
                
                IEnumerator objEnum  =  ((IEnumerable)al).GetEnumerator();

                 int  i  =   0 ;
                 while  (objEnum.MoveNext())
                 ... {
                    Object obj = objEnum.Current;
                    Console.WriteLine(" [{0}]: {1}", (Int32)i++, ((DictionaryEntry)obj).Value);
                }

由于ArrayList 排序Sort方法需要传入排序的方式，即Icompare接口。下面根据MSDN上的描述：

http://msdn2.microsoft.com/en-us/library/system.collections.icomparer.compare(VS.71).aspx

http://msdn2.microsoft.com/en-us/library/system.collections.icomparer.aspx

可知：需重写int   IComparer.Compare(Object x, Object y)方法。

Return Value

Value	Condition
Less than zero	x is less than y.
Zero	x equals y.
Greater than zero	x is greater than y.

故对以上代码实现了一个ICompare:

         public   class  myComparerClass : IComparer
         ... {

            // 比较Value，不比较key
            int IComparer.Compare(Object x, Object y)
            ...{
                DictionaryEntry X = (DictionaryEntry)x;
                DictionaryEntry Y = (DictionaryEntry)y;
                //return ((int)X.Value < (int)Y.Value ? (int)X.Value : (int)Y.Value);
                if ((int)X.Value == (int)Y.Value)
                    return 0;
                else if ((int)X.Value > (int)Y.Value)
                    return 1;
                else
                    return -1;
            }

        }