How to save data in grid with AutoAsync()?

[AntonCharov]

This is demo controller. I use EF 6. When i try to change field it's shown 500 status code. What i'm doing wrong?

        public ActionResult ShowAllRequests()
        {

            IEnumerable<Request> list = new List<Request>(new Request[] { 
                new Request() { RequestID = 1, IsDone = true, RequestName = "r1",
                    Brigade = new Brigade() { BrigadeID = 1, BrigadeName = "b1"} },
                new Request() { RequestID = 2, IsDone = true, RequestName = "r2",
                    Brigade = new Brigade() { BrigadeID = 2, BrigadeName = "b2"}}
            });            
            
            return PartialView("RequestsGrid", list);
        }

        public ActionResult GetBrigades()
        {
            IEnumerable<BrigadeComboBox> list =
                new List<BrigadeComboBox>(new BrigadeComboBox[] {
                new BrigadeComboBox { BrigadeName = "b1", Brigade = new Brigade() { BrigadeID = 1, BrigadeName = "b1"} },
                new BrigadeComboBox { BrigadeName = "b2", Brigade = new Brigade() { BrigadeID = 2, BrigadeName = "b2"} }
            });

            return this.Store(list);
        }

        public ActionResult RequestHandleChanges(StoreDataHandler handler)
        {
            List<Request> requests = handler.ObjectData<Request>();

            if (handler.Action == StoreAction.Update)
            {

            }
            
            return handler.Action == StoreAction.Update ? (ActionResult)this.Store(requests) : (ActionResult)this.Content(""); ;
        }

Models

    public class Request
    {
        [Field(FieldType = typeof(Ext.Net.Hidden))]
        public int RequestID { get; set; }
        [Display(Name = "Название")]
        public string RequestName { get; set; }
        [Display(Name = "Комментарий")]
        public string Comment { get; set; }
        [Display(Name = "Дата начала")]
        public DateTime Start { get; set; }
        [Display(Name = "Дата окончания")]
        public DateTime End { get; set; }
        [Display(Name = "Закрыто")]
        public bool IsDone { get; set; }
        [UIHint("Brigade")]
        public virtual Brigade Brigade { get; set; }
    }

    public class Brigade
    {
        [Field(FieldType = typeof(Ext.Net.Hidden), Ignore = true)]
        [ModelField(IDProperty = true, UseNull = true)]
        public int BrigadeID { get; set; }
        
        [Required]
        [PresenceValidator]
        [Display(Name = "Название")]
        public string BrigadeName { get; set; }
        public virtual ICollection<Request> Requests { get; set; }
    }

    public class BrigadeComboBox
    {
        public string BrigadeName;
        public Brigade Brigade;
    }

This is my cshtml. It loads on main page by @Html.Partail("ShowAllRequests")

@model IEnumerable<GeoSystem.Models.Request>

    <script>
        var brigadeRenderer = function (value) {
            if (!Ext.isEmpty(value)) {
                return value.BrigadeName;
            }

            return value;
        };

        var onStoreException = function (proxy, response, operation) {
            var error = operation.getError(),
                        message = Ext.isString(error) ? error : ('(' + error.status + ')' + error.statusText);

            Ext.net.Notification.show({
                iconCls: 'icon-exclamation',
                html: message + "\n<br /><b>Proxy type:</b> " + proxy.type,
                title: 'EXCEPTION',
                scrollable: 'both',
                hideDelay: 5000,
                width: 300,
                height: 200
            });
        };
    </script>

@(Html.X().Store()
            .ID("BrigadeStore")
            .Model(Html.X().Model()
                .Fields(
                    new ModelField("brigade", ModelFieldType.Object) { Mapping = "Brigade" },
                    new ModelField("BrigadeName", ModelFieldType.String) { Mapping = "BrigadeName" }
                )
            )
            .Proxy(Html.X().AjaxProxy()
                .Url(Url.Action("GetBrigades"))
                .Reader(Html.X().JsonReader().RootProperty("data"))
            )
)

@(Html.X().GridPanel()
            .ID("GridPanelRequest")
            .Store(Html.X().Store()
                .Model(Html.X().Model()
                    .Fields(
                        new ModelField("ID", ModelFieldType.Int),
                        new ModelField("RequestName"),
                        new ModelField("Comment"),
                        new ModelField("Start", ModelFieldType.Date),
                        new ModelField("End", ModelFieldType.Date),
                        new ModelField("IsDone", ModelFieldType.Boolean),
                        new ModelField()
                        {
                            Name = "Brigade",
                            Type = ModelFieldType.Object
                        }
                    )
                )
                .AutoSync(true)
                .ShowWarningOnFailure(true)
                .Listeners(l =>
                {
                    l.Exception.Fn = "onStoreException";
                    l.Exception.Buffer = 10;
                })
                .SyncUrl(Url.Action("RequestHandleChanges"))
                .DataSource(Model)
            )
            .Icon(Icon.Table)
            .Frame(true)
            .Title("Заявки")
            .Height(430)
            .Width(700)
            .StyleSpec("margin-top: 10px;")
            .ColumnModel(
                Html.X().Column()
                    .Text("Номер")
                    .DataIndex("Id"),

                Html.X().Column()
                    .Text("Название")
                    .DataIndex("RequestName")
                    .Editor(
                        Html.X().TextField().AllowBlank(false)
                    ),

                Html.X().Column()
                    .Text("Комментарий")
                    .DataIndex("Comment")
                    .Editor(
                        Html.X().TextField().AllowBlank(false)
                    ),

                Html.X().DateColumn()
                    .Text("Начало")
                    .DataIndex("Start")
                    .Editor(
                        Html.X().DateField().AllowBlank(false)
                    ),

                Html.X().DateColumn()
                    .Text("Конец")
                    .DataIndex("End")
                    .Editor(
                        Html.X().DateField().AllowBlank(false)
                    ),

                Html.X().BooleanColumn()
                    .Text("Завершено")
                    .DataIndex("IsDone")
                    .Editor(
                        Html.X().TextField().AllowBlank(false)
                    ),

                Html.X().Column()
                    .Text("Бригада")
                    .DataIndex("Brigade")
                    .Width(240)
                    .Renderer("brigadeRenderer")
                    .Editor(
                        Html.X().ComboBox()
                        .QueryMode(DataLoadMode.Remote)
                        .TriggerAction(TriggerAction.All)
                        .StoreID("BrigadeStore")
                        .ValueField("brigade")
                        .DisplayField("BrigadeName")
                    )
            )
            .Plugins(
                Html.X().CellEditing()
            )
)