对数据库数据操作，工厂方法设计模式(Factory Method)

在开发asp.net程序时，用户的数据将保存至数据库，程序与数据库之间的数据操作，会涉及到往数据库添加数据，编辑数据，更新数据和删除数据等。

本次Insus.NET介绍的是工厂方法，因此我们会从这几个操作入手。介绍工厂方法设计模式，得先从简单工厂设计模式(Simple Factory)开始，
简单工厂，有一个操作类，这个类有一个virtual方法，好让其它子类继承与重写：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

/// <summary>
/// Summary description for Operation
/// </summary>
namespace Insus.NET
{
    public class Operation
    {
        public virtual void Processing()
        {
        
        }
    }
}

数据添加类：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

/// <summary>
/// Summary description for OperationAdd
/// </summary>
namespace Insus.NET
{
    public class OperationAdd : Operation
    {
        public override void Processing()
        {
            HttpContext.Current.Response.Write("数据添加操作。");
        }
    }
}

数据编辑类：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

/// <summary>
/// Summary description for OperationEdit
/// </summary>
namespace Insus.NET
{
    public class OperationEdit : Operation 
    {
        public override void Processing()
        {
            HttpContext.Current.Response.Write("数据编辑操作。");
        }
    }
}

数据更新类：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

/// <summary>
/// Summary description for OperationUpdate
/// </summary>
namespace Insus.NET
{
    public class OperationUpdate : Operation 
    {
        public override void Processing()
        {
            HttpContext.Current.Response.Write("数据更新操作。");
        }
    }
}

数据删除类：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

/// <summary>
/// Summary description for OperationDelete
/// </summary>
namespace Insus.NET
{
    public class OperationDelete : Operation 
    {
        public override void Processing()
        {
            HttpContext.Current.Response.Write("数据删除操作。");
        }
    }
}

操作工厂类：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

/// <summary>
/// Summary description for OperationFactory
/// </summary>
namespace Insus.NET
{
    public class OperationFactory
    {
        public static Operation CreateOperate(string operate)
        {
            Operation objOperation = null;

            switch (operate)
            { 
                case "Add":
                    objOperation = new OperationAdd();
                    break;
                case "Edit":
                    objOperation = new OperationEdit();
                    break;
                case "Update":
                    objOperation = new OperationUpdate();
                    break;
                case "Delete":
                    objOperation = new OperationDelete();
                    break;
            }

            return objOperation;
        }
    }
}

OK，简单工厂完成，我们可以由简单工厂设计模式(Simple Factory)演变为工厂方法设计模式(Factory Method)。 

工厂方法设计模式，是定义一个用于创建对象的接口，让子类决定实例化哪一个类。

首先创建一个工厂接口：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

/// <summary>
/// Summary description for IOperationFactory
/// </summary>
namespace Insus.NET
{
    public interface IOperationFactory
    {
        Operation CreateOperation();
    }
}

下面分别是为添加，编辑，更新和删除各创建一个具体的工厂，并实现上面刚刚建好的工厂接口：
添加工厂类：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

/// <summary>
/// Summary description for AddFactory
/// </summary>
namespace Insus.NET
{
    public class AddFactory : IOperationFactory 
    {
        public Operation CreateOperation()
        {
          return new OperationAdd();
        }
    }
}

编辑工厂类：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

/// <summary>
/// Summary description for EditFactory
/// </summary>
namespace Insus.NET
{
    public class EditFactory : IOperationFactory 
    {
        public Operation CreateOperation()
        {
            return new OperationEdit();
        }
    }
}

更新工厂类：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

/// <summary>
/// Summary description for UpdateFactory
/// </summary>
namespace Insus.NET
{
    public class UpdateFactory : IOperationFactory 
    {
        public Operation CreateOperation()
        {
            return new OperationUpdate();
        }
    }
}

删除工厂方法：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

/// <summary>
/// Summary description for DeleteFactory
/// </summary>
namespace Insus.NET
{
    public class DeleteFactory : IOperationFactory 
    {
        public Operation CreateOperation()
        {
            return new OperationDelete();
        }
    }
}

 
这样一来，工厂方法设计模式，就是去掉简单工厂设计模式的操作工厂类，在客户端应用此设计模式，直接实例需要的哪个操作工厂，如添加工厂类还是删除工厂类等：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using Insus.NET;

public partial class FactoryMethodDemo : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        IOperationFactory factory = new UpdateFactory();  //实例更新工厂类。

        Operation operation = factory.CreateOperation();

        operation.Processing();
    }
}

 

 工厂方法设计模式源代码(.net 4.0):

 http://download.cnblogs.com/insus/CSharpNET/Insus_FactoryMethod.rar