如何使用"generic"类型构建类并将其实例化到派生类？

Question

我有这种情况

public class CustomClass
{
    public string stringTest { get; set; }
    public int numberTest { get; set; }
    public (xy) foo { get; set; }
}

这将是我的主要班级，然后：

public class Base
{
    public string somePropery { get; set; }
}
public class Derived : Base
{
    public string someOtherProperty { get; set;}
}
public class Derived2 : Base
{
    public string someHappyProperty { get; set;}
}

我想这样做：

CustomClass test = new CustomClass()
{
    foo = new Derived()
}
test.foo.someOtherProperty = "Wow!";

或

CustomClass test = new CustomClass()
{
    foo = new Derived2()
}
test.foo.someHappyProperty = "Wow!";

显然我无法将foo的类型设置为Base，并且我希望避免使用dynamic类型，什么是处理此操作的正确方法？

Answer 1

使CustomClass通用：

public class CustomClass<T>
    where T : Base
{
    public string stringTest { get; set; }
    public int numberTest { get; set; }
    public T foo { get; set; }
}

您现在可以写：

CustomClass<Derived> test = new CustomClass<Derived>()
{
    foo = new Derived()
};

test.foo.someOtherProperty = "Wow!";

Answer 2

显然我无法将foo的类型设置为Base

为什么不呢？

如果您知道它将是Derived，请将其类型设置为Derived。如果不这样做，请将其设置为Base。如果以后您想检查它是否是 a Derived并在其上设置Derived-特定成员，则可以使用is关键字：

if (test.foo is Derived)
{
    ((Derived) test.foo).someOtherProperty = "Wow!";
}