在C#中使用一个类时，分两个阶段。首先需要定义这个类，即告诉编译器这个类由什么字段和方法组成。然后（除非只使用静态方法）实例化类的一个对象。使用委托时，也需要经过这两个步骤。首先定义要使用的委托，对于委托，定义它就是告诉编译器这种类型代表了那种类型的方法，然后创建该委托的一个或多个实例。
定义委托是从delegate开始的然而它是如何运作的呢。也许弄个鼠标事件会容易理解一些，这里还是拿出书中的例子来。
using System;
namespace Wrox.ProfCSharp.AdvancedCSharp
{
delegate bool CompareOp(object lhs, object rhs);
class MainEntryPoint
{
static void Main()
{
Employee [] employees =
{
new Employee("Karli Watson", 20000),
new Employee("Bill Gates", 10000),
new Employee("Simon Robinson", 25000),
new Employee("Mortimer", (decimal)1000000.38),
new Employee("Arabel Jones", 23000),
new Employee("Avon from 'Blake's 7'", 50000)};
CompareOp employeeCompareOp = new CompareOp(Employee.RhsIsGreater);
BubbleSorter.Sort(employees, employeeCompareOp);
for (int i=0 ; i<employees.Length ; i++)
Console.WriteLine(employees[i].ToString());
Console.ReadLine();
}
}
class Employee // : object
{
private string name;
private decimal salary;
public Employee(string name, decimal salary)
{
this.name = name;
this.salary = salary;
}
public override string ToString()
{
return string.Format(name + ", {0:C}", salary);
}
public static bool RhsIsGreater(object lhs, object rhs)
{
Employee empLhs = (Employee) lhs;
Employee empRhs = (Employee) rhs;
return (empRhs.salary > empLhs.salary) ? true : false;
}
}
class BubbleSorter
{
static public void Sort(object [] sortArray, CompareOp gtMethod)
{
for (int i=0 ; i<sortArray.Length ; i++)
{
for (int j=i+1 ; j<sortArray.Length ; j++)
{
if (gtMethod(sortArray[j], sortArray[i]))
{
object temp = sortArray[i];
sortArray[i] = sortArray[j];
sortArray[j] = temp;
}
}
}
}
}
}
using System;
namespace Wrox.ProfCSharp.AdvancedCSharp
{
delegate bool CompareOp(object lhs, object rhs);
class MainEntryPoint
{
static void Main()
{
Employee [] employees =
{
new Employee("Karli Watson", 20000),
new Employee("Bill Gates", 10000),
new Employee("Simon Robinson", 25000),
new Employee("Mortimer", (decimal)1000000.38),
new Employee("Arabel Jones", 23000),
new Employee("Avon from 'Blake's 7'", 50000)};
CompareOp employeeCompareOp = new CompareOp(Employee.RhsIsGreater);
BubbleSorter.Sort(employees, employeeCompareOp);
for (int i=0 ; i<employees.Length ; i++)
Console.WriteLine(employees[i].ToString());
Console.ReadLine();
}
}
class Employee // : object
{
private string name;
private decimal salary;
public Employee(string name, decimal salary)
{
this.name = name;
this.salary = salary;
}
public override string ToString()
{
return string.Format(name + ", {0:C}", salary);
}
public static bool RhsIsGreater(object lhs, object rhs)
{
Employee empLhs = (Employee) lhs;
Employee empRhs = (Employee) rhs;
return (empRhs.salary > empLhs.salary) ? true : false;
}
}
class BubbleSorter
{
static public void Sort(object [] sortArray, CompareOp gtMethod)
{
&