如何限制添加到派生类的项的类型

本文关键字：类型 派生 何限制 添加 | 更新日期: 2023-09-27 18:25:10

我有继承自BaseClass的DerivedClass。我想利用BaseCollection类，它覆盖InsertItem方法，所以我定义了DerivedCollection并从BaseCollection继承。问题是，DerivedCollection允许同时添加DerivedClass和BaseClass类型。我只想允许将DerivedClass类型添加到DerivedCollection中。我错过了什么？

public class BaseClass
{
    public static string MyString;
}
public class BaseCollection<T> : Collection<BaseClass> where T : BaseClass
{
    protected override void InsertItem(int index, BaseClass item)
    {
        throw new UnauthorizedAccessException("I'm sorry Dave, I'm afraid I can't do that.");
    }
}
public class DerivedClass : BaseClass
{
    public static int MyInteger;
}
public class DerivedCollection : BaseCollection<DerivedClass>
{
}

如何限制添加到派生类的项的类型

  1. 将BaseCollection<T>更改为从Collection<T>继承，而不是从Collection<BaseClass>继承
  2. 适当更改InsertItem的参数
public class BaseCollection<T> : Collection<T> where T : BaseClass
{
    protected override void InsertItem (int index, T item)
    {
        throw new UnauthorizedAccessException("I'm sorry Dave, I'm afraid I can't do that.");
    }
}

您只想允许T:

protected override void InsertItem(int index, T item)
{
    throw new UnauthorizedAccessException("I'm sorry Dave, I'm afraid I can't do that.");
}

您还必须从Collection<T>而不是Collection<BaseClass>继承

您需要覆盖InsertItem，如下所示：

public class DerivedCollection : BaseCollection<DerivedClass>
{
protected override void InsertItem(int index, DerivedClass item)
    {
        base.InsertItem(index, item);
    }
}
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