C# ArrayList.BinarySearch 小问题 --- 必须是按顺序存储才可以这样查找

ArrayList.BinarySearch (Object)

使用默认的比较器在整个已排序的 ArrayList 中搜索元素，并返回该元素从零开始的索引。

ArrayList.BinarySearch (Object, IComparer)	使用指定的比较器在整个已排序的 ArrayList 中搜索元素，并返回该元素从零开始的索引。
ArrayList.BinarySearch (Int32, Int32, Object, IComparer)	使用指定的比较器在已排序 ArrayList 的某个元素范围中搜索元素，并返回该元素从零开始的索引。由 .NET Compact Framework 支持。

---强调一点。因为是 2分查找。所以必须是按照顺序存放值，否则出错。

有2个方式实现 IComparer 和类自己实现一个接口 system 中的

D:\c_\arraylist>Test
person CompareTo(object obj) this person is 4 -- objthis person is 3
person CompareTo(object obj) this person is 2 -- objthis person is 3
person CompareTo(object obj) this person is 104 -- objthis person is 3
find   person p3 = new person(3); -3   比较后得不到结果严重问题
-----
person CompareTo(object obj) this person is 4 -- objthis person is 5
find   person p3 = new person(3); 6
-----
person CompareTo(object obj) this person is 4 -- objthis person is 1
person CompareTo(object obj) this person is 2 -- objthis person is 1
find person p1 = new person(1); 0
-----
person CompareTo(object obj) this person is 4 -- objthis person is 104
person CompareTo(object obj) this person is 5 -- objthis person is 104
person CompareTo(object obj) this person is 1 -- objthis person is 104
person CompareTo(object obj) this person is -88 -- objthis person is 104
find      person p6 = new person(104); -10 -- 比较后得不到结果严重问题
0 this person is 1
1 this person is 2
2 this person is 104
3 this person is 3
4 this person is 4
5 this person is 122
6 this person is 5
7 this person is 1
8 this person is -88

using System;
using System.Collections;
using System.Collections.Generic;

public class Test

{

public class person : IComparable

{
        public int age = 0;
        public person(int i)

{
            this.age = i;

        }
        public override string ToString()

{

            return "this person is " + age;

        }

        public int CompareTo(object obj)

{

            Console.WriteLine(" person  CompareTo(object obj)  " + this.ToString() + " -- obj" + obj.ToString());

            if (obj is person)

{
                person temp = (person)obj;

                return  age.CompareTo(temp.age);
            }

            throw new ArgumentException("object is not a CompareTo ");
        }

    }

    public static void Main(string[] args)

{


        ArrayList list = new ArrayList(300);


        person p1 = new person(1);
        person p2 = new person(2);
        person p3 = new person(3);
        person p4 = new person(4);
        person p5 = new person(5);
        person p0 = new person(-88);

        person p6 = new person(104);
        person p7 = new person(122);


        list.Add(p1);
        list.Add(p2);
        list.Add(p6);

        list.Add(p3);
        list.Add(p4);
        list.Add(p7);

        list.Add(p5);
       list.Add(p1);
       list.Add(p0);

        /**//*

       Console.WriteLine(list[1]);
       list.Remove(1); //  1  will be object  for method input paramt
       Console.WriteLine(list[1]);
       list.RemoveAt(1);
       Console.WriteLine(list[1]);
        */

       /**//*
        *
        *  ArrayList list0 = new ArrayList(2);

       list0.Add(new person(12));

        * list.AddRange(list0);
       Console.WriteLine(" 合并集合 AddRange  新的集合都在最后 " + list[2]);
       Console.WriteLine(" 老集合的包含的数量    --添加新的以用不修改老的集合 " + list0.Count);
       */

       Console.WriteLine("find   person p3 = new person(3); " + list.BinarySearch(p3));

       Console.WriteLine("-----");

       Console.WriteLine("find   person p3 = new person(3); " + list.BinarySearch(p5));

       Console.WriteLine("-----");

       Console.WriteLine("  find  person p1 = new person(1);  " + list.BinarySearch(p1));

       Console.WriteLine("-----");

       Console.WriteLine("  find      person p6 = new person(104); " + list.BinarySearch(p6));

        for (int i = 0; i < list.Count; i++ )

{
            Console.WriteLine(i + " " + list[i].ToString() );

        }

    }

}

/**/ /*

Summary:
Compares two objects and returns a value indicating whether one is less than, equal to, or greater than the other.

Parameters:
x: The first object to compare.
y: The second object to compare.

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

Exceptions:
System.ArgumentException: Neither x nor y implements the System.IComparable interface.-or- x and y are of different types and neither one can handle comparisons with the other.

*/
class personIComparer : System.Collections.IComparer

{

public int Compare(object x, object y)

{

         Test.person p1 = x as Test.person;
         Test.person p2 = y as Test.person;

        if ( p1 == null )

{
           //??

        }

         if (p1.age ==  p2.age )

{
return 0;
}else

{
if (p1.age > p2.age )

{

return 1;
}else

{
                 return -1;

             }
         }


    }

}

/**/ /*

public class Temperature : IComparable {
    /// <summary>
    /// IComparable.CompareTo implementation.
    /// </summary>
    public int CompareTo(object obj) {
        if(obj is Temperature) {
            Temperature temp = (Temperature) obj;

            return m_value.CompareTo(temp.m_value);
        }

        throw new ArgumentException("object is not a Temperature");
    }

    // The value holder
    protected int m_value;

    public int Value {
        get {
            return m_value;
        }
        set {
            m_value = value;
        }
    }

    public int Celsius {
        get {
            return (m_value-32)/2;
        }
        set {
            m_value = value*2+32;
        }
    }
}

*/

C# ArrayList.BinarySearch 小问题 --- 必须是按顺序存储 才可以这样 查找