add the formview inside the composit control

Question

dear friends , I created the composit control and put the formview inside that , I got this exception :

Unable to cast object of type 'System.Web.UI.LiteralControl' to type 'System.Web.UI.WebControls.Table'.

after set this line

if (!Page.IsPostBack) _template.InstantiateIn(_fv);

would you please help me to find the good solution . here is my code :

[ToolboxData("<{0}:SimpleForm runat=server></{0}:SimpleForm>")]
[ParseChildren(true)]
[Designer("Web.UI.Form, Web.UI", typeof(IDesigner))]
[AspNetHostingPermission(SecurityAction.Demand, Level = AspNetHostingPermissionLevel.Minimal)]
        public class SimpleForm : CompositeControl
        {
            readonly FormView _fv;
            public SimpleForm()
            {
                _fv = new FormView { DefaultMode = FormViewMode.Edit, Width = Unit.Percentage(100) };
            }

            private IBindableTemplate _template = null;

            [PersistenceMode(PersistenceMode.InnerProperty),
            TemplateContainer(typeof(FormView), BindingDirection.TwoWay)]
            public IBindableTemplate FormTemplate
            {
                get { return _template; }
                set { _template = value; }
            }

            protected override void OnLoad(EventArgs e)
            {
                if (_template != null)
                {
                    _fv.InsertItemTemplate = _fv.EditItemTemplate = _template;
                    if (!Page.IsPostBack) _template.InstantiateIn(_fv);
                }

                base.OnLoad(e);
            }

            protected override void CreateChildControls()
            {
                Controls.Add(_fv);
            }
            protected override HtmlTextWriterTag TagKey
            {
                get
                {
                    return HtmlTextWriterTag.Div;
                }
            }

            internal void GetDesignTimeHtml()
            {
                EnsureChildControls();
            }
        }