C＃泛型抽象类从抽象泛型类继承 [英] c# Abstract Generic Class inheriting from Abstract Generic Class

问题描述

我试图创建一个抽象泛型类从另一个抽象泛型类继承。

I'm trying to create an abstract generic class which inherits from another abstract generic class.

下面是我迄今为止

public abstract class BaseClass {
    public long Id { get; private set; }

    public BaseClass(long id) {
        this.Id = id;
    }
}

public abstract class BaseClass<T> : BaseClass where T : BaseClass {
    protected BaseClass(long id)
        : base(id) {

    }

    public static T Get(long id) {
        T item;
        return TryGet(id, out item) ? item : default(T);
    }

    public static bool TryGet(long id, out T item) {
        item = null; // This is where I call the cache but for this example I've removed so it will compile
        if (item != null) { return true; }
        else {
            // Call TryGetFallback method
            return false;
        }
    }

    protected abstract T TryGetFallback(long id);
}


public abstract class DerivedClass : BaseClass<DerivedClass> {
    public String Name { get; private set; }

    public DerivedClass(long id, String name)
        : base(id) {
        this.Name = name;
    }
}

public class DerivedDerivedClass : DerivedClass {

    protected override DerivedDerivedClass TryGetFallback(long id) {
        // Handle the try get fallback
    }
}

在DerivedDerivedClass的TryGetFallback方法将导致编译。误差

The TryGetFallback method on the DerivedDerivedClass causes a compiler error.

推荐答案

首先，你需要修复你的的BaseClass< T> 。实施没有递归类型约束

First you need to fix your BaseClass<T> implementation to not have a recursive type constraint.

public abstract class BaseClass<T> : BaseClass where T : new() {
    //snip
}

然后你就可以在你的派生类中使用它，比如我会使其使用 INT 泛型类型参数：

public abstract class DerivedClass : BaseClass<int> {
    //snip
}

现在，如果你编译它会警告您'DerivedDerivedClass不实现继承的抽象成员的BaseClass< INT> .TryGetFallback（长）

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