C# 依赖注入那些事儿

原文地址：http://www.cnblogs.com/leoo2sk/archive/2009/06/17/1504693.html

里面有一个例子差了些代码，补全后贴上。

3.1.3 依赖获取

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml;

//定义了三个接口 IWindow IButton ITextBox
namespace DependencyLocate
{
    internal interface IWindow
    {
        String ShowInfo();
    }
    internal interface IButton
    {
        String ShowInfo();
    }
    internal interface ITextBox
    {
        String ShowInfo();
    }
}

//实现接口 IWindow， 实现类 WindowsWindow、MacWindow
namespace DependencyLocate
{
    internal sealed class WindowsWindow : IWindow
    {
        public String Description { get; private set; }

        public WindowsWindow()
        {
            this.Description = "Windows风格窗体";
        }

        public String ShowInfo()
        {
            return this.Description;
        }
    }

    internal sealed class MacWindow : IWindow
    {
        public String Description { get; private set; }

        public MacWindow()
        {
            this.Description = " Mac风格窗体";
        }

        public String ShowInfo()
        {
            return this.Description;
        }
    }
}

//实现接口 IButton， 实现类 WindowsButton、MacButton
namespace DependencyLocate
{
    internal sealed class WindowsButton : IButton
    {
        public String Description { get; private set; }

        public WindowsButton()
        {
            this.Description = "Windows风格按钮";
        }

        public String ShowInfo()
        {
            return this.Description;
        }
    }

    internal sealed class MacButton : IButton
    {
        public String Description { get; private set; }

        public MacButton()
        {
            this.Description = " Mac风格按钮";
        }

        public String ShowInfo()
        {
            return this.Description;
        }
    }
}

//实现接口 ITextBox， 实现类 WindowsTextBox、MacTextBox
namespace DependencyLocate
{
    internal sealed class WindowsTextBox : ITextBox
    {
        public String Description { get; private set; }

        public WindowsTextBox()
        {
            this.Description = "Windows风格文本框";
        }

        public String ShowInfo()
        {
            return this.Description;
        }
    }

    internal sealed class MacTextBox : ITextBox
    {
        public String Description { get; private set; }

        public MacTextBox()
        {
            this.Description = " Mac风格文本框";
        }

        public String ShowInfo()
        {
            return this.Description;
        }
    }
}

namespace DependencyLocate
{
    internal interface IFactory
    {
        IWindow MakeWindow();

        IButton MakeButton();

        ITextBox MakeTextBox();
    }
}

namespace DependencyLocate
{
    internal sealed class WindowsFactory : IFactory
    {
        public IWindow MakeWindow()
        {
            return new WindowsWindow();
        }

        public IButton MakeButton()
        {
            return new WindowsButton();
        }

        public ITextBox MakeTextBox()
        {
            return new WindowsTextBox();
        }
    }
}

namespace DependencyLocate
{
    internal sealed class MacFactory : IFactory
    {
        public IWindow MakeWindow()
        {
            return new MacWindow();
        }

        public IButton MakeButton()
        {
            return new MacButton();
        }

        public ITextBox MakeTextBox()
        {
            return new MacTextBox();
        }
    }
}

namespace DependencyLocate
{
    internal static class FactoryContainer
    {
        public static IFactory factory { get; private set; }

        /// <summary>
        /// 静态构造函数：
        ///     是一个特殊的函数，将在其他所有方法执行之前以及变量或属性被第一次访问之前执行。
        ///     这个构造函数是属于类的，而不是属于哪里实例的，就是说这个构造函数只会被执行一次。
        ///     也就是在创建第一个实例或引用任何静态成员之前，由.NET自动调用。
        ///     可以使用该函数来初始化静态变量，不应该使用实例构造函数初始化静态变量。
        /// 地址：https://www.cnblogs.com/aimi/p/5499711.html
        /// </summary>
        static FactoryContainer()
        {
            XmlDocument xmlDoc = new XmlDocument();
            xmlDoc.Load("Config.xml");
            XmlNode xmlNode = xmlDoc.ChildNodes[].ChildNodes[].ChildNodes[];

            if ("Windows" == xmlNode.Value)
            {
                factory = new WindowsFactory();
            }
            else if ("Mac" == xmlNode.Value)
            {
                factory = new MacFactory();
            }
            else
            {
                throw new Exception("Factory Init Error");
            }
        }
    }
}

namespace DependencyLocate
{
    class Program
    {
        static void Main(string[] args)
        {
            IFactory factory = FactoryContainer.factory;
            IWindow window = factory.MakeWindow();
            Console.WriteLine("创建 " + window.ShowInfo());
            IButton button = factory.MakeButton();
            Console.WriteLine("创建 " + button.ShowInfo());
            ITextBox textBox = factory.MakeTextBox();
            Console.WriteLine("创建 " + textBox.ShowInfo());

            Console.ReadLine();
        }
    }
}