创建对象时需要考虑是否实现比较器
1、基础有对象的地方，一般都会存在比较。在此根据一个Salary列表实现对象比较的例子。Salary类需要实现接口IComparable。
class Salary:IComparable
{ public string Name { get; set; } public int baseSalary { get; set; } public int Bonus { get; set; } public int CompareTo(object obj)
{
Salary salary = obj is Salary ? obj as Salary : null; if(salary==null)
{ throw new Exception("类型不同，无法比较");
} if(baseSalary>salary.baseSalary)
{ return 1;
} else if(baseSalary==salary.baseSalary)
{ return 0;
} else
{ return -1;
} //以上代码可有以下代码代替，使用整型默认比较方法 //return baseSalary.CompareTo(salary.baseSalary); }
}实现接口IComparable后，可以根据baseSalary对Salary集合对象排序。在Main函数中代码如下：
public static void Main()
{
ArrayList companySalary = new ArrayList();
companySalary.Add(new Salary() { Name = "Mike", baseSalary = 3000,Bonus=1000 });
companySalary.Add(new Salary() { Name = "Rose", baseSalary = 2000, Bonus = 6000 });
companySalary.Add(new Salary() { Name = "Tom", baseSalary = 5000, Bonus = 5000 });
companySalary.Add(new Salary() { Name = "Jeffry", baseSalary = 1000, Bonus = 2000 });
companySalary.Add(new Salary() { Name = "Steve", baseSalary = 4500, Bonus = 1900 });
companySalary.Sort(); foreach (Salary salary in companySalary)
{
Console.WriteLine("{0}t baseSalary: {1}tBonus: {2}", salary.Name, salary.baseSalary,salary.Bonus);
}}但是，此处实现相当于比较局限，局限与只能使用baseSalary排序，不能使用其他方式排序。如果使用Bonus进行排序，就需要改变源码。接口IComparer的作用可以避免这类问题。
2、IComparer接口使用IComparer接口实现一个自定义比较器：
class BonusComparer : IComparer
{ int IComparer.Compare(object x, object y)
{
Salary salary1 = x is Salary ? x as Salary : null;
Salary salary2 = y is Salary ? y as Salary : null; return salary1.Bonus.CompareTo(salary2.Bonus);
}
}在主控端调用时排序时，需要在Sort方法中传入一个实现了IComparer接口的比较器对象：companySalary.Sort(new BonusComparer())。以此实现可以根据需要，实现多种比较。
3、泛型实现在前面，使用了性能不高的ArrayList类。在泛型出来之后，需要尽量使用泛型集合。在CompareTo和Compare和函数中，需要对对象进行转型，比较影响性能，尤其是对大型集合进行排序时，性能影响非常明显。而泛型的出现，可以避免运行时的转型。因此，上面的代码全部更换为泛型类型：
class Program
{ public static void Main()
{
List companySalary = new List();
companySalary.Add(new Salary() { Name = "Mike", baseSalary = 3000, Bonus = 1000 });
companySalary.Add(new Salary() { Name = "Rose", baseSalary = 2000, Bonus = 6000 });
companySalary.Add(new Salary() { Name = "Tom", baseSalary = 5000, Bonus = 5000 });
companySalary.Add(new Salary() { Name = "Jeffry", baseSalary = 1000, Bonus = 2000 });
companySalary.Add(new Salary() { Name = "Steve", baseSalary = 4500, Bonus = 1900 });
companySalary.Sort(); foreach (Salary salary in companySalary)
{
Console.WriteLine("{0}t baseSalary: {1}tBonus: {2}", salary.Name, salary.baseSalary, salary.Bonus);
}
companySalary.Sort(new BonusComparer());//提供一个默认比较器
foreach (Salary salary in companySalary)
{
Console.WriteLine("{0}t baseSalary: {1}tBonus: {2}", salary.Name, salary.baseSalary, salary.Bonus);
}
}
}class Salary : IComparable{ public string Name { get; set; } public int baseSalary { get; set; } public int Bonus { get; set; } public int CompareTo(Salary other)
{ if (other == null)
{ throw new Exception("类型不同，无法比较");
} if (baseSalary > other.baseSalary)
{ return 1;
} else if (baseSalary == other.baseSalary)
{ return 0;
} else
{ return -1;
} //以上代码可有以下代码代替，使用整型默认比较方法 //return baseSalary.CompareTo(other.baseSalary); }
}class BonusComparer : IComparer{ public int Compare(Salary x, Salary y)
{ return x.Bonus.CompareTo(y.Bonus);
}
} 4、Linq实现针对前面实现排序方法时，需要实现多个接口，新增了方法使得代码入侵性太高。可扩展性差，对于有新的排序要求，就必须实现新的比较器。使用Linq，可以实现遍历、筛选、投影集合等功能。
class Program
{ public static void Main()
{
List companySalary = new List();
companySalary.Add(new Salary() { Name = "Mike", baseSalary = 3000, Bonus = 1000 });
companySalary.Add(new Salary() { Name = "Rose", baseSalary = 2000, Bonus = 6000 });
companySalary.Add(new Salary() { Name = "Tom", baseSalary = 5000, Bonus = 5000 });
companySalary.Add(new Salary() { Name = "Jeffry", baseSalary = 1000, Bonus = 2000 });
companySalary.Add(new Salary() { Name = "Steve", baseSalary = 4500, Bonus = 1900 }); var baseSalarySort = from salary in companySalary orderby salary.baseSalary select salary; foreach (Salary salary in baseSalarySort)
{
Console.WriteLine("{0}t baseSalary: {1}tBonus: {2}", salary.Name, salary.baseSalary, salary.Bonus);
} var bonusSort = from salary in companySalary orderby salary.Bonus select salary; foreach (Salary salary in bonusSort)
{
Console.WriteLine("{0}t baseSalary: {1}tBonus: {2}", salary.Name, salary.baseSalary, salary.Bonus);
}
}
}class Salary
{ public string Name { get; set; } public int baseSalary { get; set; } public int Bonus { get; set; }
} Linq可以带来很大的便利性，但需要掌握比较器、迭代器、索引器的原理，以便更好地理解Linq的思想。
