Why event "MoveNext" is not fired in this server control?

[gocoding]

I have a composite sever control with a gridview and a custom navigation toolbar, could you take a look, why events of button MoveNext in the toolbar is not fired? Thanks in advance,

public class cSCGridNavigatorPanel: WebControl, INamingContainer
{ 
  ..
  protected ImageButton fbtnNext;
  ..
  public event ImageClickEventHandler btnNext_Click;
  protected void fbtnNext_Click(object sender, ImageClickEventArgs e)
  {
    if (btnNext_Click != null)
      btnNext_Click(sender, e);
  }


  ..
  protected override void CreateChildControls() 
  { 
    ..
    fbtnFirst = new ImageButton(); 
    fbtnFirst.Click += new ImageClickEventHandler(fbtnFirst_Click);	
    this.Controls.Add(fbtnFirst);    
    ..
  }
  
  protected override void Render(HtmlTextWriter writer)
  {
    EnsureChildControls();
    AddAttributesToRender(writer);  
    ..
    fbtnNext.RenderControl(writer);
    ..
  }
}


public class cSCGridWithNavigatorPanel: WebControl, INamingContainer 
{
  public cSCGridWithNavigatorPanel() {}
  ...
  GridView fDataGrid;
  GridNavigatorPanel fNavigatorPanelTop;
   
  protected void MoveNext(object sender, System.Web.UI.ImageClickEventArgs e)
  {  		
     if (fDataGrid.CurrentPageIndex < fDataGrid.PageCount-1) 
       fDataGrid.CurrentPageIndex += 1;
  }

  protected override void CreateChildControls() 
  {
    this.DataBind(); 
    fNavigatorPanelTop = new cSCGridNavigatorPanel(this.ClientID,"fNavigatorPanelBottom");
    fNavigatorPanelTop.ID = "fNavigatorPanelTop";    
    ..
    fNavigatorPanelTop.btnNext_Click += new ImageClickEventHandler(MoveNext);
    ..
    this.Controls.Add(fNavigatorPanelTop);
  }

  protected override void Render(HtmlTextWriter writer)
  {
    EnsureChildControls();
    AddAttributesToRender(writer);
    ..
    fNavigatorPanelTop.RenderControl(writer);
    ..
  }
}