ASP.NET的适配器设计模式(Adapter)

前天有一网友问及有关设计模式的适配器模式(Adapter)时，说不太好理解。让Insus.NET能否举个简单的例子来说明一下。下面的动画是Insus.NET做出来的效果:

上面的演示，两个灯的规格一样，要求输入的电压为15伏。
Light1是直接使用，而Light2是使用Adapter(电源适配器)。因此Light1只能接收15伏的电压，小于15伏，会提示电压过低，如果超过了15伏，Light1肯定被烧坏。
Light2使用了电源适配器，它接收15伏至220的电压，在这电压范围之内，电源适配器会把电压转为15的电压。小于15伏，会提示电压过低，如果超过了220伏，适配器被烧坏。

好，我们程序开始，先创建一个灯Light的类：

Light.cs

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

/// <summary>
/// Summary description for Light
/// </summary>
namespace Insus.NET
{
    public class Light
    {
        private int _InputVoltage = 15;

        public int InputVoltage
        {
            get { return _InputVoltage; }
            set
            {
                if (value < 15)
                    throw new Exception("电压过低。");
                else if (value > 15)
                    throw new Exception("危险！电压过大灯烧坏。");
                else
                    value = 15;

                _InputVoltage = value;
            }
        }

        public Light()
        {
            //
            // TODO: Add constructor logic here
            //
        }
    }
}

再创建一个灯的电源适配器：

PowerAdapter.cs

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

/// <summary>
/// Summary description for PowerAdapter
/// </summary>
namespace Insus.NET
{
    public class PowerAdapter : Light
    {
        Light _Light;

        public PowerAdapter(Light light)
        {
            this._Light = light;
        }

        public int InputVoltage
        {
            get
            {
                return _Light.InputVoltage;
            }
            set
            {
                if (value < 15)
                    throw new Exception("电压过低。");
                else if (value > 220)
                    throw new Exception("危险！电压过大电源适配器烧坏。");
                else
                    value = 15;

                _Light.InputVoltage = value;
            }
        }
    }
}

如何测试它们，我们得模拟一个环境，创建一个网页Default.aspx：

Default.aspx

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
    <script type="text/javascript">
        function isNumeric(keyCode) {
            return ((keyCode >= 48 && keyCode <= 57) || keyCode == 8)
        }
    </script>
</head>
<body>
    <form id="form1" runat="server">
        <table>
            <tr>
                <td align="right">插座电压</td>
                <td colspan="2">
                    <asp:TextBox ID="TextBox1" runat="server" onkeydown="return isNumeric(event.keyCode);" Text="220"></asp:TextBox></td>
            </tr>
            <tr>
                <td align="right">开关</td>
                <td colspan="2">
                    <asp:CheckBox ID="CheckBoxSwitch" runat="server" AutoPostBack="true" OnCheckedChanged="CheckBoxSwitch_CheckedChanged" /></td>
            </tr>
            <tr>
                <td align="right">灯</td>
                <td>
                    <fieldset style=" 200px;">
                        <legend>Light 1
                        </legend>
                        <asp:Image ID="Image1" runat="server" ImageUrl="Images/Light_C.gif" Width="36" Height="55" /><br />
                        <asp:Label ID="Label1" runat="server" Text=""></asp:Label>
                    </fieldset>
                </td>
                <td>
                    <fieldset style=" 250px;">
                        <legend>Light 2
                        </legend>
                        <asp:Image ID="Image2" runat="server" ImageUrl="Images/Light_C.gif" Width="36" Height="55" /><br />
                        <asp:Label ID="Label2" runat="server" Text=""></asp:Label>
                    </fieldset>
                </td>
            </tr>
        </table>
    </form>
</body>
</html>

接下来，看看开关的事开与关的事件，有详细的注解：

Default.aspx.cs

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 _Default : System.Web.UI.Page
{
    string offLight = "~/Images/Light_C.gif";
    string onLight = "~/Images/Light_O.gif";

    protected void Page_Load(object sender, EventArgs e)
    {

    }

    protected void CheckBoxSwitch_CheckedChanged(object sender, EventArgs e)
    {
        var cb = (CheckBox)sender;

        //插座缺少电压为220伏
        int input = Convert.ToInt32(string.IsNullOrEmpty(this.TextBox1.Text.Trim()) ? "220" : this.TextBox1.Text.Trim());

        //开关打开
        if (cb.Checked)
        {
            try
            {
               //实例一个电灯
                Light light = new Light();

                //插入插座，使用插座电压
                light.InputVoltage = input;

                //电灯被打开
                this.Image1.ImageUrl = onLight;

                //显示正常输出电压
                this.Label1.Text = light.InputVoltage.ToString();
            }
            catch (Exception ex)
            {
               //如果电压不正常，电灯打不开或是被烧坏。
                this.Image1.ImageUrl = offLight;

                //显示异常信息。
                this.Label1.Text = ex.Message;
            }

            try
            {              
                Light light = new Light();

                //使用电源适配器
                PowerAdapter pa = new PowerAdapter(light);
                pa.InputVoltage = input;

                this.Image2.ImageUrl = onLight;
                this.Label2.Text = pa.InputVoltage.ToString();

            }
            catch (Exception ex)
            {
                this.Image2.ImageUrl = offLight;
                this.Label2.Text = ex.Message;
            }

            this.TextBox1.Enabled = false;
        }
        //开关关闭
        else
        {
            this.TextBox1.Text = string.Empty;
            this.TextBox1.Enabled = true;
            this.Image1.ImageUrl = offLight;
            this.Image2.ImageUrl = offLight;
        }
    }
}

11：44分，补充下面内容，有网友问及演示完整代码(.NET Framework 4.0)

http://download.cnblogs.com/insus/ASPDOTNET/AdapterDemo.rar