Get property name in DisplayNameAttribute derived class

Using c#, .net 4.5.

I have a class with some properties with DisplayNameEx attribute, which is derived from DisplayNameAttibute:

public class Settings
{
    [DisplayNameEx("User")]
    public UserData User { get; set; }
}

public class DisplayNameExAttribute : DisplayNameAttribute
{
    public DisplayNameExAttribute(string id)
    {

    }
}

I pass as string id ALLWAYS name of my property, so it would be easier writing code this way:

public class Settings
{
    [DisplayNameEx()]
    public UserData User { get; set; }
}

But I don't know, how could I resolve a property name here:

public class DisplayNameExAttribute : DisplayNameAttribute
{
    public DisplayNameExAttribute()
    {
        // what is the property name, which called this constructor?
    }
}

In addition, it would be also a class name needed (Settings in my case) here.