you can use event method to pass values from Child to Parent.
Suppose We have two classes names Parent and Child. Then create an event in Child class like
public delegate ValueChangedHandler(DataTable DT);
public event ValueChangedHandler ValueChanged;
Now raise this event from Button event click
//DT: Suppose it is the desired object to return
Now come to Parent class, here you have to handle this event like
Child objChild=new Child();
objChild.ValueChanged += new ValueChangedHandler(objChild_ValueChanged);
New method will create with the name "objChild_ValueChanged" like
void objChild_ValueChanged(DataTable DT)
//TODO: Now you can use this value which in coming from Child class.