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c#泛型和反射的设计应用
 
 
文章录入：浣花溪    责任编辑：snow  122 
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From 心灵魔术师's blog
在设备操作面板的设计中总会有一类固定的按钮和操作惯例，但如果每做一个项目都写一套同样的代码实在很没效率的事。

    设备的操作按钮大多数都会包含启动、暂停、停止这三个按钮，软件界面中也同样需要这三类按钮，软件需要根据设备的状态

来禁用或启用不同的按钮组合。比如刚启动软件时，启动按钮开启，暂停和停止按钮禁用等等。

    一般设计情况下是用Button,也有的设计会用ToolStripButton，为了使其兼容更多的控件，所以采用了泛型。代码如下：

   
    public enum OperateState { Run, Pause, Stop };

    public class OperateStateRule where T : ToolStripItem
    {
        private T start;
        private T pause;
        private T stop;

        private OperateState state = OperateState.Stop;

        private OperateState State
        {
            get { return state; }
            //set { state = value; }
        }

        public OperateStateRule(T _start, T _pause, T _stop)
        {
            start = _start;
            pause = _pause;
            stop = _stop;

            Update(OperateState.Stop);
        }

        public void Update(OperateState _state)
        {
            state = _state;
            try
            {
                switch (state)
                {
                    case OperateState.Stop:
                        start.Enabled = true;
                        pause.Enabled = false;
                        stop.Enabled = false;
                        break;
                    case OperateState.Run:
                        start.Enabled = false;
                        pause.Enabled = true;
                        stop.Enabled = true;
                        break;
                    case OperateState.Pause:
                        start.Enabled = true;
                        pause.Enabled = false;
                        stop.Enabled = true);
                        break;
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }
    }

    调用示例：

     ToolStripButton btnStart；
     ToolStripButton btnPause；
     ToolStripButton btnStop；

     //生成对象时绑定相应的按钮
     OperateStateRule rule = new  OperateStateRule(btnStart,btnPause,btnStop);
     //在Click事件里更新状态
      private void btnStart_Click(object sender, EventArgs e)
        {
            rule.Update(OperateState.Run);
        }

        private void btnPause_Click(object sender, EventArgs e)
        {
            rule.Update(OperateState.Pause);
        }

        private void btnStop_Click(object sender, EventArgs e)
        {
            rule.Update(OperateState.Stop);
        }
    

    在类声明上有个where T : ToolStripItem语句，这个是c#类型约束，如果不加这个约束，编译器会报错找不到Enabled属性，

但有个问题Button和ToolStripButton这两个类不是同一个基类派生，所以无法兼容使用这2个类，因为必须要有这个约束，使得c++

的一些泛型做法受到限制。

    那还有没有更好的方法来达到理想的效果呢，答案是有的，就是反射。看下面改进的代码例子：

    public enum OperateState { Run, Pause, Stop };

    public class OperateStateRule
    {
        private T start;
        private T pause;
        private T stop;

        private OperateState state = OperateState.Stop;

        private OperateState State
        {
            get { return state; }
            //set { state = value; }
        }

        public OperateStateRule(T _start, T _pause, T _stop)
        {
            start = _start;
            pause = _pause;
            stop = _stop;

            Update(OperateState.Stop);
        }
        //通过反射设置属性值
        private void SetEnabled(T obj, bool value)
        {
            obj.GetType().InvokeMember("Enabled", BindingFlags.SetProperty, null, obj, new object[] { value});
        }
        public void Update(OperateState _state)
        {
            state = _state;
            try
            {
                switch (state)
                {
                    case OperateState.Stop:
                        SetEnabled(start, true);
                        SetEnabled(pause, false);
                        SetEnabled(stop, false);
                        break;
                    case OperateState.Run:
                        SetEnabled(start, false);
                        SetEnabled(pause, true);
                        SetEnabled(stop, true);
                        break;
                    case OperateState.Pause:
                        SetEnabled(start, true);
                        SetEnabled(pause, false);
                        SetEnabled(stop, true);
                        break;
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }
    }
   
    可以看到已经不需要where子句来约束类型，通过借助泛型和反射实现了更好通用性，不但能使用Button和ToolStripButton，

还能使用其他的控件，只要有Enabled属性即可。
 

摘自红色黑客联盟(www.7747.net) 原文：http://www.7747.net/kf/201002/44832.html