How to export TreeGrid with client-side data in Angular?

//app.component.html
<ej-treegrid #TreeGridControl id="TreeGridControl"
[toolbarSettings]="toolbarsettings"
  (toolbarClick)="toolbarclick($event)"
//… >
</ej-treegrid>

//app.component.ts
export class AppComponent {
            public editsettings;
            public toolbarsettings;
            public constructor() {
                this.editsettings = {
                    allowAdding: true,
                    allowEditing: true,
                    allowDeleting: true
                };
                this.toolbarsettings = {
                    showToolbar: true,
                    toolbarItems: ['excelExport', 'pdfExport']
                };
            }
    @ViewChild('TreeGridControl') treegrid: EJComponents<any, any>;
            toolbarclick(args) {
                var treeObj = this.treegrid.widget;
                treeObj.model["exportData"] = JSON.stringify(treeObj.dataSource());
 
                if (args.itemName == "Excel Export") {
                    treeObj.exportGrid = treeObj["export"];
                    treeObj.exportGrid('http://localhost:50280/api/TreeGrid/ExcelExport', "", true);
                    args.cancel = true;
                }
                else {
                    treeObj.exportGrid = treeObj["export"];
                    treeObj.exportGrid('http://localhost:50280/api/TreeGrid/PdfExport', "", true);
                    args.cancel = true;
                }
            }

[AcceptVerbs("Post")]
        public void ExcelExport()
        {
            string gridProperty = HttpContext.Current.Request.Params["TreeGridModel"];
            ExcelExport exp = new ExcelExport();
 
 
            TreeGridProperties gridProp = this.ConvertGridObject(gridProperty);
            exp.Export(gridProp, (IEnumerable)exportData, "Export.xlsx", ExcelVersion.Excel2010, new TreeGridExportSettings() { Theme = ExportTheme.FlatSaffron });
        }
 
        [AcceptVerbs("Post")]
        public void PdfExport()
        {
            string gridProperty = HttpContext.Current.Request.Params["TreeGridModel"];
            PdfExport exp = new PdfExport();
            TreeGridProperties gridProp = this.ConvertGridObject(gridProperty);
            exp.Export(gridProp, (IEnumerable)exportData, new TreeGridExportSettings() { Theme = ExportTheme.FlatSaffron }, "Export");
        }
public TreeGridProperties ConvertGridObject(string gridProperty)
        {
            JavaScriptSerializer serializer = new JavaScriptSerializer();
            IEnumerable div = (IEnumerable)serializer.Deserialize(gridProperty, typeof(IEnumerable));
            TreeGridProperties gridProp = new TreeGridProperties();
            foreach (KeyValuePair<string, object> ds in div)
            {
                var property = gridProp.GetType().GetProperty(ds.Key, BindingFlags.Instance | BindingFlags.Public | BindingFlags.IgnoreCase);
                if (ds.Key == "exportData")
                {
                    string str = Convert.ToString(ds.Value);
                    exportData = JsonConvert.DeserializeObject<IEnumerable<HierachicalData>>(str);
                    continue;
                }
 
                if (property != null)
                {
                    Type type = property.PropertyType;
                    string serialize = serializer.Serialize(ds.Value);
                    object value = serializer.Deserialize(serialize, type);
                    property.SetValue(gridProp, value, null);
                }
            }
            return gridProp;
        }