From元素如何访问列表

Question

I have one element from list, how to access this list count from element, like this:

    public void Setup()
    {
    var myList = new List<T>();
    myList.add(new T(1));
    myList.add(new T(2));
    myList.add(new T(3));
    myList.add(new T(4));


    var myElement = myList.Last();

    MyFunctionReflection(myElement);
    }



    public void MyFunctionReflection(T element)
    {
    var countElements = ????? //How determine elements in Ilist from element using reflection
   Console.Write("the list that owns the element, contains {0} elements.",countElements);
    }

Answer 1

For all practical purposes, this is not possible.

Theoretically, using unsafe code, it might be possible to walk through the entire program's memory space, look for every single List object, see if it contains a reference to the object in question, and then access it's count. While this might be theoretically possible though, it's almost certainly not an acceptable solution to virtually any problem, and would be prohibitively difficult/time consuming to try to code.

Answer 2

You can't.

You will have to either pass-in the count, or pass-in a reference to the list:

public void MyFunctionReflection(T element, int count) ...

or

public void MyFunctionReflection(T element, IList<T> list) ...

Answer 3

There is no direct link between an element and the List to which it belongs.

What you could do, is when you instantiate your element, pass it a reference to the List and make it available through a property on the element.

You Element class:

public class Element
{
    public List<Element> ParentList;

    public Element(int value, List<Element> parent)
    {
        ...
        ParentList = parent;
    }
}

Then in your main code:

var myList = new List<T>();
myList.add(new T(1, myList));
myList.add(new T(2, myList));
myList.add(new T(3, myList));

then later:

var countElements = myElement.ParentList.Count; // ParentList is the reference to the List<T> that was passed to the constructor.

Cheers