[英]C# cast from IEnumerable<T> to T
Can anyone explain that :谁能解释一下:
I already checked source code for IEnumerable<> & IEnumerable and found nothing FYI this doesn't work with List我已经检查了 IEnumerable<> 和 IEnumerable 的源代码,但没有发现这不适用于 List
class Program
{
public class Person
{
public long Age { get; set; }
}
static void Main(string[] args)
{
IEnumerable<Person> list = new List<Person>();
((Person)list).Age = 5;
}
}
There isn't a check at compile time for interface cast to class.在编译时没有检查接口转换为类。
As you can see you can even compile that:如您所见,您甚至可以编译:
class Program
{
static void Main(string[] args)
{
IPizza<Pasta> ao = new Pizza<Pasta>();
((Pasta)ao).MyProperty = 10;
}
}
public interface IPizza<T>
{
}
public class Pizza<T> : IPizza<T>
{
}
public class Pasta
{
public int MyProperty { get; set; }
}
Interface casted to class will be evaluated in runtime.转换为类的接口将在运行时进行评估。
Infact, if you use as type Pizza<Pasta>
instead of IPizza<Pasta>
it will give you a compile error:事实上,如果你使用
Pizza<Pasta>
而不是IPizza<Pasta>
作为类型,它会给你一个编译错误:
class Program
{
static void Main(string[] args)
{
Pizza<Pasta> ao = new Pizza<Pasta>();
((Pasta)ao).MyProperty = 10;
}
}
public interface IPizza<T>
{
}
public class Pizza<T> : IPizza<T>
{
}
public class Pasta
{
public int MyProperty { get; set; }
}
I tried something not too useful but "correct" for both C# compiler & runtime我为 C# 编译器和运行时尝试了一些不太有用但“正确”的东西
I got my answer我得到了答案
public class Person
{
public long Age { get; set; }
}
static void Main(string[] args)
{
IEnumerable<Person> list;
list = new Father();
((Father)list).Age = 5;
}
public class Father : Person, IEnumerable<Person>
{
public IEnumerator<Person> GetEnumerator()
{
throw new NotImplementedException();
}
IEnumerator IEnumerable.GetEnumerator()
{
throw new NotImplementedException();
}
}
}
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