Passing objects and a list of objects by reference in C#

I have a delegate that modifies an object. I pass an object to the delegate from a calling method, however the calling method does not pick up these changes. The same code works if I pass a List as the object.

I thought all objects were passed by reference so any modifications would be reflected in the calling method. Is that correct?

I can modify my code to pass a ref object to the delegate. But I am wondering why this is necessary. Or is it?

public class Binder
{
    protected delegate int MyBinder<T>(object reader, T myObject);

    public void BindIt<T>(object reader, T myObject)
    {
        //m_binders is a hashtable of binder objects
        MyBinder<T> binder = m_binders["test"] as MyBinder<T>;
        int i = binder(reader, myObject);
    }
}

public class MyObjectBinder
{
    public MyObjectBinder()
    {
        m_delegates["test"] = new MyBinder<MyObject>(BindMyObject);
    }

    private int BindMyObject(object reader, MyObject obj)
    {
        obj = new MyObject
        {
            //update properties
        };
        return 1;
    }
}

///calling method in some other class
public void CallingMethod()
{
    MyObject obj = new MyObject();

    MyObjectBinder binder = new MyObjectBinder();
    binder.BindIt(myReader, obj); //don't worry about myReader

    //obj should show reflected changes
}

Update:

I am now passing objects by ref to the delegate as I am instantiating a new object inside BindMyObject.

protected delegate int MyBinder<T>(object reader, ref T myObject);