I am loading data in a chart and I would like to have "Loading..." preloader until the data loads. I cannot find a way to do this.
Can anyone help please?

X.Chart()
                                .ID("ChartTopCustomers")
                                .Shadow(true)
                                .Width(400)
                                .Height(200)
                                .StyleSpec("background:#fff;")
                                .Animate(true)
                                .Store(X.Store()
                                    .Data(Model)
                                    .Model(X.Model()
                                        .Fields(
                                            X.ModelField().Name("Reference"),
                                            X.ModelField().Name("Name"),
                                            X.ModelField().Name("Data")
                                        )
                                    )
                                    .Proxy(X.AjaxProxy()
                                        .Url(Url.Action("GetTopCustomers", "List"))
                                        .Reader(X.JsonReader().Root("data"))
                                    )
                                    
                                )
                                .Axes(
                                    X.NumericAxis()
                                        .Fields("Data")
                                        .Grid(true)
                                        .Title("")
                                        .Minimum(0)
                                        .Label(X.AxisLabel()
                                            .Renderer(r => r.Handler = "return Ext.util.Format.number(value, '0,0');")
                                        ),
                                    X.CategoryAxis()
                                        .Position(Position.Bottom)
                                        .Fields("Reference")
                                        .Title("")
                                )
                                .Series(X.ColumnSeries()
                                    .Axis(Position.Left)
                                    .Highlight(true)
                                    .XField("Name")
                                    .YField("Data")
                                    .Tips(X.ChartTip()
                                        .TrackMouse(true)
                                        .Width(240)
                                        .Height(28)
                                        .Renderer(r => r.Handler = "this.setTitle(storeItem.get('Name') + ': ' + storeItem.get('Data'));")
                                    )
                                    .Label(X.SeriesLabel()
                                        .Display(SeriesLabelDisplay.InsideEnd)
                                        .Field(new[] { "Data" })
                                        .Orientation(Orientation.Horizontal)
                                        .Color("#333")
                                        .TextAnchor("middle")
                                        .Renderer(r => r.Handler = "return Ext.util.Format.number(value, '0');")
                                    )
                                )