ASP.NET/csharp:FileUpload inside AJAX Update panel

To make it working it's required :
1.Created interface:

public interface ITriggerable {
void RegisterPostbackTrigger(Control  parent,Control trigger);
}

2.implement this interface on page containing ajax update panel:

public void RegisterPostbackTrigger(Control  parent,Control button){
       PostBackTrigger trigger = new PostBackTrigger();
       trigger.ControlID =((Button) button).UniqueID;
       UpdatePanel1.Triggers.Add(trigger);
}

3.Add button inside of control as trigger:

protected override void OnInit(EventArgs e){
 base.OnInit(e);
    ((ITriggerable)this.Page).RegisterPostbackTrigger(this, btnRename);
}