Question

Say I have a simple class like this:

public class ReferenceChanger<T> 
{
    public T SavedElement { get; private set; }

    public ReferenceChanger(T elementToSave)
    {
        SavedElement = elementToSave;
    }

    // This method would change the original variable (given as a constructor argument)
    public void SetNewReference(T newElement)
    {
        SavedElement = newElement;
    }
}

This class saves an element given to its constructor, whatever element is. However, the “SavedElement” (its backing field) is a reference to the object given at the time of instance creation.

Is there any way to save a reference to a variable (as with using ref keyword), so that if the original item passed to the constructor changes, the SavedElement would automatically reflect the change, almost as if the object was passed with the ref keyword? (Even if I use the ref keyword, I would not be able to save the reference that way.)

Updated to make intentions more clear:

public class ExampleClass 
{
    public List<int> Numbers { get; set; }
}

public static void Main()
{
    ExampleClass temp = new ExampleClass();
    temp.Numbers = new List<int>() { 1, 2, 3 }; 

    ReferenceChanger<List<int>> changer = new ReferenceChanger<List<int>>(temp.Numbers);
    // Here, a reference to the List<int> instance (containing 1,2,3) is stored in changer's SavedElement

    // Then I do this:
    changer.SetNewReference(new List<int>() { 5, 6, 7 });

    // Now, only changer's SavedElement was changed, but temp's property Numbers was not changed.
    // Is there a way to change the temp's property Numbers from the changer?
}

Answer 1

Sounds like you’re looking for TypedReference and the __makeref keyword.

Warning: they’re poorly documented and not in the standardized part of C#.

There’s a lot more information in this question.