C# 使用派生类的方法覆盖带有基类的抽象方法

Question

似乎找不到解决方案，也不明白为什么这是不可能的：

（第一行代码似乎不想在我的浏览器上正确格式化）

namespace Definitions
{
    public interface iCore
    {
        public ChannelBase GetChannel(UrlBase url);
    }

    public abstract class Core : iCore
    {
        public abstract ChannelBase GetChannel(UrlBase url);
    }

    public class ChannelBase
    {
        public ChannelBase(iCore core) 
        { }
    }

    public class UrlBase
    {
        public UrlBase(iCore core) 
        { }
    }
}

namespace Processing
{
    /// Error Thrown:
    //Severity Code    Description Project File Line    Suppression State
    //Error CS0534  'MyCore' does not implement inherited abstract member 'Core.GetChannel(UrlBase)'


    public class MyCore : Definitions.Core
    {
        /// It suggests this Implementation:
        //public override Definitions.ChannelBase GetChannel(Definitions.UrlBase url) { }

        /// I need this to work, but how ?
        public override MyChannel GetChannel(MyUrl url) 
        { 
             /// This is where i would really need that MyUrl.MyExtraPropertyIneed !
            return null; 
        }
    }

    public class MyChannel : Definitions.ChannelBase
    {
        public MyChannel(MyCore core) : base(core) 
        { }
    }

    public class MyUrl : Definitions.UrlBase
    {
        public MyUrl(MyCore core)  : base(core)
        {
            MyExtraPropertyIneed = "I NEED this property"
        }
        
        public string MyExtraPropertyIneed { get; private set; }
        // PS this is a basic example, but i really can't have this property in the Base Class, the Derrived class gets info from online and does "stuff"
    }
}

“public override MyChannel GetChannel(MyUrl url)”总是抛出错误“‘MyCore’没有实现继承的抽象成员‘Core.GetChannel(UrlBase)’”

如何解决这个问题？

期望派生类被接受 请注意，例如我使用了不同的命名空间，但实际上每个命名空间都是一个单独的项目。

Answer 1

像这样编辑

GetChannel()

的签名

public override ChannelBase GetChannel(UrlBase url)
    {
        // implementation
        return new MyChannel(this);
    }

Answer 2

函数覆盖不允许签名不同。如果要返回子类，可能具有与抽象方法相同的签名，但返回子类实例，然后在方法的调用者中转换为子类。

public override ChannelBase GetChannel(UrlBase url) 
{ 
    return new MyChannel(); 
}

In the caller method,

var obj = new MyCore().GetChannel();

这应该有效。