c# - 类型 'TNestedInterface' 必须可转换为 'INestedInterfaceTest' 才能将其用作参数 'TNestedInterface'

Question

public interface INestedInterfaceTest<TChildType>
    where TChildType : INestedInterfaceTest<TChildType>
{
     List<TChildType> children { get; set; }
}

public abstract class NestedInterfaceTest : INestedInterfaceTest<NestedInterfaceTest>
{
    public List<NestedInterfaceTest> children { get; set; }

    public TNestedInterface GetNestedInterface<TNestedInterface>()
        where TNestedInterface : NestedInterfaceTest, new()
    {
        return GateWay<TNestedInterface>.GetNestedInterface();
    }
}

public class GateWay<TNestedInterface>
    where TNestedInterface : class, INestedInterfaceTest<TNestedInterface>, new()
{
    public static TNestedInterface GetNestedInterface()
    {
        return new TNestedInterface();
    }
}

抽象类中的 GetNestedInterface 方法出错。错误消息是:类型“TNestedInterface”必须可转换为“INestedInterfaceTest”才能将其用作通用类“GateWay”中的参数“TNestedInterface”。

但是...，我的抽象类 NestedInterfaceTest 实现了 INestedInterfaceTest 接口(interface)。我在这里缺少什么？

以下确实有效，没有递归接口(interface)实现:

public interface INestedInterfaceTest
{
}

public abstract class NestedInterfaceTest : INestedInterfaceTest
{
    public List<NestedInterfaceTest> children { get; set; }

    public TNestedInterface GetNestedInterface<TNestedInterface>()
        where TNestedInterface : NestedInterfaceTest, new()
    {
        return GateWay<TNestedInterface>.GetNestedInterface();
    }
}

public class GateWay<TNestedInterface>
    where TNestedInterface : class, INestedInterfaceTest, new()
{
    public static TNestedInterface GetNestedInterface()
    {
        return new TNestedInterface();
    }
}

好像是递归实现的时候出错了

Answer 1

您缺少对 GetNestedInterface<>() 的通用约束.将其更改为:

public TNestedInterface GetNestedInterface<TNestedInterface>()
    where TNestedInterface : 
        NestedInterfaceTest, 
        INestedInterfaceTest<TNestedInterface>, // new
        new()
{
    return GateWay<TNestedInterface>.GetNestedInterface();
}

注意第二个约束是新的。