C＃ - 泛型和继承的问题
C＃ - 泛型和继承的问题
提问于 2018-05-28 01:15:01
我遇到了继承和泛型的问题。这是说明我的问题的代码：
namespace TestApplication
{
public class MyClass<T>
{
private T field;
public MyClass(T field)
{
this.field = field;
}
}
public class MyIntClass : MyClass<int>
{
public MyIntClass(int field)
: base(field)
{
}
}
}
当我尝试做这样的事情时：
MyClass<int> sth = new MyClass<int>(10);
MyIntClass intsth = (MyIntClass) sth;
我收到转换异常： Invalid cast exception. Unable to cast 'TestApplication.MyClass`1[System.Int32]' to 'TestApplication.MyIntClass'.
还有什么我不能创建操作符：
public static implicit operator MyIntClass(MyClass<int> myClass)
因为：'TestApplication.MyIntClass.implicit operator TestApplication.MyIntClass(TestApplication.MyClass)': user-defined conversions to or from a base class are not allowed
回答 2
Stack Overflow用户
发布于 2018-05-28 10:13:08
MyClass<int> foo = new MyIntClass();
MyIntClass bar = (MyIntClass)foo; // this works.
Assume：
class Base {
int x;
}
class Derived : Base {
int y;
}
Base foo = new Base();
Derived bar = (Derived)foo;
Stack Overflow用户
发布于 2018-05-28 11:12:07
using System;
class Base {}
class Child : Base {}
class Test
{
static void Main()
{
Base b = new Base();
// This will throw an exception
Child c = (Child) b;
}
}
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/-100000084
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