c# - 在 C# 中，派生管理器类如何返回派生类的实例而不重新实现所有内容？

Question

在下面的示例中，如何让 SpecialThingDB 返回 SpecialThings 列表，而不必像我一样重新实现 ThingDB 的所有方法？

public class Thing
{
    public readonly string Color;
    public readonly int Weight;

    public Thing(string color, int weight)
    {
        Color = color;
        Weight = weight;
    }

    // Some methods
}

public class ThingDB
{
    public List<Thing> GetByColor(string color)
    {
        var things = new List<Thing>();
        // Get things from the database's Thing table
        return things;
    }

    public List<Thing> GetByWeight(int weight)
    {
        var things = new List<Thing>();
        // Get things from the database's Thing table
        return things;
    }
}

public class SpecialThing : Thing
{
    public SpecialThing(string color, int weight) : base(color, weight)
    {
    }

    // Some special methods
}

public class SpecialThingDB : ThingDB
{
    // How do I have GetByColor and GetByWeight return SpecialThings here
    // without completely re-implementing the base methods like below?

    public List<SpecialThing> GetByColor(string color)
    {
        var specialThings = new List<SpecialThing>();
        // Get things from the database's Thing table
        return specialThings;
    }

    public List<SpecialThing> GetByWeight(int weight)
    {
        var specialThings = new List<SpecialThing>();
        // Get things from the database's Thing table
        return specialThings;
    }
}

此外，除了为数据库中的每个表使用两个类(一个代表一条记录，另一个是管理器类)之外，是否还有更好的模式？

更新

给出解决方案(谢谢，the_joric!)，以下是我对上述代码所做的更改:

public class ThingDB<T> where T : Thing
{
    public List<T> GetByColor(string color)
    {
        var things = new List<T>();
        // Do some database stuff to fill things by color
        return things;
    }

    public List<T> GetByWeight(int weight)
    {
        var things = new List<T>();
        // Do some database stuff to fill things by weight
        return things;
    }
}

public class SpecialThing : Thing
{
    public SpecialThing(string color, int weight)
        : base(color, weight)
    {
    }

    // Some special methods
}

public class SpecialThingDB : ThingDB<SpecialThing> { }

public class ThingDB : ThingDB<Thing> { } // For backward-compatibility

Answer 1

您可以使用泛型。就像下面这样:

public class ThingDB<T> where T: Thing
{
    public List<T> GetByColor(string color)
    {
        var things = new List<T>();
        // Get things from the database's Thing table
        return things;
    }

    public List<T> GetByWeight(int weight)
    {
        var things = new List<T>();
        // Get things from the database's Thing table
        return things;
    }
}