.NET常用设计模式——迭代器模式

迭代器模式(Iterator)

封装多个元素
使用户正确使用
遍历内部内容

总结Iterator



使用标准接口遍历列表/集合
封装操作
提供后期操功能作扩展

应用实例



using System;

using System.Data;

using System.Data.SqlClient;

using System.Collections;

namespace CSDesingPattern

{

public class Employee

{

private int EmpId = 0;

private string EmpName = "";

public int ID

{

get

{

return EmpId;

}

set

{

EmpId = value;

}

}

public string Name

{

get

{

return EmpName;

}

set

{

EmpName = value;

}

}

}

//集合类

public class Employees

{

private ArrayList arEmp = new ArrayList();

private int EmpCount;

public Employees()

{

SqlConnection cn = new SqlConnection

("server=localhost;database=northwind;uid=sa;pwd=windows");

SqlCommand cmd = new SqlCommand

("select EmployeeID,FirstName,BirthDate from Employees", cn);

cn.Open();

SqlDataReader dr = cmd.ExecuteReader();

while (dr.Read())

{

Employee obj = new Employee();

obj.ID = dr.GetInt32(0);

obj.Name = dr.GetString(1);

arEmp.Add(obj);

}

EmpCount = arEmp.Count;

}

public Employee Item(int idx)

{

return (Employee)arEmp[idx];

}

public int Count

{

get

{

return EmpCount;

}

}

}

//迭代器实现类

public class EmployeesIterator

{

private int intCurrent;

private Employees mObj;

public EmployeesIterator(ref Employees obj)

{

intCurrent = 0;

mObj = obj;

}

public Employee MoveFirst()

{

intCurrent = 0;

return mObj.Item(intCurrent);

}

public Employee MoveLast()

{

intCurrent = mObj.Count - 1;

return mObj.Item(intCurrent);

}

public Employee MoveNext()

{

intCurrent = intCurrent + 1;

if (intCurrent >= mObj.Count)

{

intCurrent = mObj.Count - 1;

throw new Exception("索引超过下限");

}

return mObj.Item(intCurrent);

}

public Employee MovePrev()

{

//throw new Exception (intCurrent.ToString());

intCurrent = intCurrent - 1;

if (this.intCurrent == -1)//||this.intCurrent <=0)

{

intCurrent = 1;

throw new Exception("索引超过上限,当前为" + intCurrent.ToString());

}

return mObj.Item(intCurrent);

}

}

}