.NET初学者架构设计指南（三）设计模式

Code
class SignalFactory
{
    public static Signal CreateSignal(string dev, string sig)
    {
        //获取信号的定义
        string sql = 
            "SELECT * FROM SIG WHERE DEV='" + dev + "' AND SIG='" + sig + "'";
        //查数据库表
        
        //判断需要创建的类型
        Signal signal = null;
        if (type == 'A') 
        {
            signal = new AnalogSignal();
        }
        else if (type == 'S') 
        {
            signal = new StateSignal();
        }
        else if (type == 'P')
        {
            signal = new PresumeSignal();
        }
        else 
        {
            return null;
        }
        
        //设置Signal的配置参数
        signal.SetUnit(unit);
        signal.SetStateDescription(state_description);
        signal.SetPresumeFormule(presume_formule)
        
        return signal;
    }
}

Signal sig = SignalFactory.CreateSignal(dev, sig);
string s = sig.GetDisplayString();