从PropertyInfo获取对象引用

Question

I have a little problem, below my code:

public class A
{
    public string ObjectA { get; set; }
}

public void Run()
{
    A a = new A();
    a.ObjectA = "Test number 1";

    BindingFlags flags = BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic;
    PropertyInfo myPropertyInfo = a.GetType().GetProperty("ObjectA", flags);
    object myNewObject = myPropertyInfo.GetValue(a);// Here should be reference

    a.ObjectA = "Test number 2";//After this line value myNewObject continued "Test number 1"
}

So my value myNewObject must be in output "Test number 2". Is there any way? It is this at all possible?

Answer 1

Wrong!

You're getting the string rather than the instance of A using reflection.

Changing A.ObjectA doesn't change the string reference. Actually, you're setting a different string to the backing string class field by the ObjectA property...

Auto-properties are syntactic sugar to avoid explicitly declaring class fields to properties which perform nothing when getting or setting their values:

// For example:
public string Text { get; set; }

// is...
private string _text;
public string Text { get { return _text; } set { _text = value; } }

Now turn your code into regular one (no reflection):

A a = new A();
a.ObjectA = "hello world";

object myNewObject = a.ObjectA;

// Do you think now that myNewObject should change...? :)
a.ObjectA = "goodbye";

Is there any way? It is this at all possible?

No.

Maybe you can simulate this behavior using a Func<T> ...

Func<object> myNewObjectGetter = () => myPropertyInfo.GetValue(a);

Now, whenever you call myNewObjectGetter() you're going to get the most fresh value of the whole property. BTW, this still doesn't address the impossible!

Answer 2

Is there any way?

No. You can't put a reference to a property into an object variable. Such a variable can only hold a normal value, such as the string you put into it.

That answers the question as asked. You can clarify what you want to achieve and maybe we can suggest a better way.

Answer 3

Probably there is no solution but I show some code

public class MyRows
{
    public string Key { get; set; }
    public int Id { get; set; }
    public object Val { get; set; }
}

public abstract class BasicDTO
{
    public int? Id { get; private set; }

    public PropertyInfo[] PropertyDTO;
    protected Type myType;

    public BasicDTO()
    {
        Load();
        BindingFlags flags = BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic;
        PropertyDTO = myType.GetProperties(flags);
    }
}

public class CustomerDTO : BasicDTO
{
    public string Surname { get; set; }
    public string Phone { get; set; }

    public CustomerDTO() { }

    protected override void Load()
    {
        myType = typeof(CustomerDTO);         
    }
}

Now my basic method

public void Run(BasicDTO dto)
{
    PropertyInfo pi = dto.PropertyDTO.Where(x => x.Name == "Surname").SingleOrDefault();
    MyRows mr = new MyRows();
    mr.Val = pi.GetValue(dto);//Here I need reference
}

When I change CustomerDTO.Surname my value mr.Val it must also be changed. As I wrote above, it is probably impossible, but maybe anybody have a idea.

BTW: Value mr.Val I use only for binding (WPF). So maybe you have any other suggestions, how solve problem. I will be grateful for your help