c# - 如何编写一个好的离线-在线调度程序

Question

假设我有这样的场景:我有 2 个信息存储库，我想访问这两个存储库，但是最好将决定使用哪个存储库的任务留给 common class。

目标是使用与我在下面编写的代码类似的东西来完成此操作，但这听起来很糟糕:

where TOnline : class
where TOffline : class
where TContract : class

当然我可以忽略这一点，但基本上我要问的是如何停止使用反射并进行输入。也许有任何设计模式推荐？

代码(如果您将其复制/粘贴到替换 Program 类的控制台应用程序中，您应该能够运行该示例)

using CustomerDispatcher = DispatcherProxy<CustomerOnline, CustomerOffline, ICustomer>;

public interface ICustomer
{
    string Get(int id);
}

public class CustomerOnline : ICustomer
{
    public string Get(int id)
    {
        // Get From intranet DB
        return "From DB";
    }
}

public class CustomerOffline : ICustomer
{
    public string Get(int id)
    {
        // Get From local storage
        return "From local storage";
    }
}

public class DispatcherProxy<TOnline, TOffline, TContract>
    where TOnline : class
    where TOffline : class
    where TContract : class
{
    public TContract Instance { get; set; }

    public bool IsConnected { get; set; }

    public DispatcherProxy()
    {
        // Asume that I check if it's connected or not
        if (this.IsConnected)
            this.Instance = (TContract)Activator.CreateInstance(typeof(TOnline));
        else
            this.Instance = (TContract)Activator.CreateInstance(typeof(TOffline));
    }
}

class Program
{
    static void Main(string[] args)
    {
        var customerDispatcher = new CustomerDispatcher();

        Console.WriteLine("Result: " + customerDispatcher.Instance.Get(1));

        Console.Read();
    }
}

提前致谢!

Answer 1

您可以添加 new() 约束:

public class DispatcherProxy<TOnline, TOffline, TContract>
    where TOnline : class, new()
    where TOffline : class, new()
    where TContract : class //isn't TContract an interface?
{
    public TContract Instance { get; set; }

    public bool IsConnected { get; set; }

    public DispatcherProxy()
    {
        // Asume that I check if it's connected or not
        if (this.IsConnected)
            this.Instance = new TOnline() as TContract;
        else
            this.Instance = new TOffline() as TContract;
    }
}