How to assign the data from asynchronous (async) service in Syncfusion ASP.NET Core reportviewer?

public partial class HomeController : Controller, IReportController
{
    private IMemoryCache _cache;
    private IHostingEnvironment _hostingEnvironment;
 
    public HomeController(IMemoryCache memoryCache, IHostingEnvironment hostingEnvironment)
    {
        _cache = memoryCache;
        _hostingEnvironment = hostingEnvironment;
    }
 
    public ActionResult Index()
    {
        return View();
    }
 
    public IActionResult Error()
    {
        return View();
    }
 
    [HttpPost]
    public object PostReportAction([FromBody] Dictionary<string, object> jsonResult)
    {
        if (jsonResult.ContainsKey("CustomData"))
        {
            var paramValue = jsonResult["CustomData"];
        }
        return ReportHelper.ProcessReport(jsonResult, this, this._cache);
    }
 
    [ActionName("GetResource")]
    [AcceptVerbs("GET")]
    public object GetResource(ReportResource resource)
    {
        return ReportHelper.GetResource(resource, this, _cache);
    }
 
    [HttpPost]
    public object PostFormReportAction()
    {
        return ReportHelper.ProcessReport(null, this, this._cache);
    }
 
    public void OnInitReportOptions(ReportViewerOptions reportOption)
    {
        string basePath = _hostingEnvironment.WebRootPath;
        FileStream inputStream = new FileStream(basePath + @"\ReportData\Region.rdlc", FileMode.Open, FileAccess.Read);
        reportOption.ReportModel.Stream = inputStream;
    }
 
    public async void OnReportLoaded(ReportViewerOptions reportOption)
    {
        if (reportOption.ReportModel.ProcessingMode == ProcessingMode.Local)
        {
            reportOption.ReportModel.DataSources.Clear();
            var ReportData = await GetData();
            reportOption.ReportModel.DataSources.Add(new ReportDataSource { Name = "StoreSales", Value = ReportData });
        }
    }
 
    private async Task<List<StoreSales>> GetData()
    {
        List<StoreSales> sales = new List<StoreSales>();
        StoreSales strSal = null;
        strSal = new StoreSales()
        {
            SalesOrderID = 43659,
            TotalDue = 23153.2339,
            CustomerID = 29825,
            StateProvinceCode = "GA",
            Store = "Better Bike Shop"
        };
        sales.Add(strSal);
        strSal = new StoreSales()
        {
            SalesOrderID = 43663,
            TotalDue = 472.3108,
            CustomerID = 29565,
            StateProvinceCode = "CA",
            Store = "World Bike Discount Store"
        };
        sales.Add(strSal);
        strSal = new StoreSales()
        {
            SalesOrderID = 43673,
            TotalDue = 4216.0258,
            CustomerID = 29844,
            StateProvinceCode = "NH",
            Store = "Seventh Bike Store"
        };
        sales.Add(strSal);
        strSal = new StoreSales()
        {
            SalesOrderID = 43675,
            TotalDue = 6434.0848,
            CustomerID = 29827,
            StateProvinceCode = "MO",
            Store = "First Bike Store"
        };
        sales.Add(strSal);
 
        return await Task.Run(() => sales);
    }
}
 
public class StoreSales
{
    public int SalesOrderID { get; set; }
    public double TotalDue { get; set; }
    public int CustomerID { get; set; }
    public string Store { get; set; }
    public string StateProvinceCode { get; set; }
}