protected override void CreateChildControls() { InternalHiddenField l = new InternalHiddenField(); l.ID = this.ControlID + "_textboxInternal"; this.Controls.Add(l); KeyPressEventExtender ext = new KeyPressEventExtender(); ext.ControlID = this.ControlID; ext.TargetControlID = this.ControlID + "_textboxInternal"; this.Controls.Add(ext); base.CreateChildControls(); }