How would a file download that is initiated via a DirectEvent work in Ext.NET v7?

This forum post explains how it worked in a previous version. I can't find any 'IsUpload' property for a click event handler in v7 though. I assume things have changed somewhat in the framework since that post was written.

In the code-behind of a Razor page, I want to create a button that, when clicked, will invoke a Direct Event for the page. Something like this:

                new Button
                {
                    Text = "Export",
                    DirectEvents =
                    {
                        new ClickDirectEventHandler
                        {
                            Url = "ExportToExcel", // How to set page handler instead?                           
                            ExtraParams =
                            {
                                new DirectEventParameter
                                {
                                    Key = "TabName",
                                    Value = tabName
                                }
                            }
                        }
                    }
                }
The handler for the Direct Event looks something like this:

        [Direct]
        public async Task<IActionResult> OnPostExportToExcelAsync([FromBody] ExcelExportData request)
        {
            byte[] fileContents = DoWorkToCreateExcelFile();

            return File(
                fileContents,
                "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
                "MyFile.xslx");
        }
Thanks

Paul