Question

public class Base
{
}
public class Rabbit : Base
{
}
public abstract class OO
{
    public abstract ICollection<T> Test<T>() where T : Base;
}
public class LOL : OO
{
    public override ICollection<T> Test<T>()
    {
        return new Collection<Rabbit>();
    }
}

这种类的形成会产生以下错误。

＆＃39; System.Collections.ObjectModel.Collection＆＃39;到＆＃39; System.Collections.Generic.ICollection＆＃39;。存在显式转换（您是否错过了演员？）

知道如何解决这个问题吗？

Answer 1

试试这个：

public class LOL : OO
    {
        public override ICollection<T> Test<T>()
        {
            return (ICollection<T>) new Collection<Rabbit>();
        }
    }

Answer 2

public class Base
{
}
public class Rabbit : Base
{
}
public abstract class OO
{
    public abstract ICollection<T> Test<T>() where T : Base;
}
public class LOL : OO
{
    public override ICollection<T> Test<T>()
    {
        return new Collection<T>();
    }
}

或

public class Base
{
}
public class Rabbit : Base
{
}
public abstract class OO
{
    public abstract ICollection<T> Test<T>() where T : Base;
}
public class LOL : OO
{
    public override ICollection<T> Test<T>()
    {
        return new Collection<Rabbit>() as ICollection<T>;
    }
}

通用方法覆盖c＃存在显式转换（您是否错过了转换？）错误

2 个答案: