How to export the WinUI DataGrid (SfDataGrid) to excel with RowHeader?

WinUI DataGrid (SfDataGrid) does not provide the support to export the row header. You can export the row header column by using Worksheet.InsertColumn method to insert a column manually in ExcelSheet and make customization in the inserted column.

private void btnExportToExcelClicked(object sender, RoutedEventArgs e)
{            
    var options = new DataGridExcelExportOptions(); 
    var excelEngine = dataGrid.ExportToExcel(dataGrid.View, options);
    var workBook = excelEngine.Excel.Workbooks[0];
    IWorksheet sheet = workBook.Worksheets[0];

    // Inserting a new column to the left of the first column
    sheet.InsertColumn(1, 1, ExcelInsertOptions.FormatDefault);
    
    // Get the number of rows count
    var rowcount = this.dataGrid.RowGenerator.Items.Count;

    for (int i = 1; i < rowcount; i++)
    {
        // Inserting the row index in the first row
        sheet.Range["A" + (i + 1).ToString()].Number = i;
    }

    MemoryStream stream = new MemoryStream();
    workBook.SaveAs(stream);
    Save(stream, "Sample");

    async void Save(MemoryStream stream, string filename)
    {
        StorageFile stFile;

        if (!(Windows.Foundation.Metadata.ApiInformation.IsTypePresent("Windows.Phone.UI.Input.HardwareButtons")))
        {
            FileSavePicker savePicker = new FileSavePicker();
            savePicker.DefaultFileExtension = ".xlsx";
            savePicker.SuggestedFileName = filename;
            savePicker.FileTypeChoices.Add("Excel Documents", new List<string>() { ".xlsx" });
            var hwnd = System.Diagnostics.Process.GetCurrentProcess().MainWindowHandle;
            WinRT.Interop.InitializeWithWindow.Initialize(savePicker, hwnd);
            stFile = await savePicker.PickSaveFileAsync();
        }
        else
        {
            StorageFolder local = ApplicationData.Current.LocalFolder;
            stFile = await local.CreateFileAsync(filename, CreationCollisionOption.ReplaceExisting);
        }
        if (stFile != null)
        {
            using (IRandomAccessStream zipStream = await stFile.OpenAsync(FileAccessMode.ReadWrite))
            {
                //Write the compressed data from the memory to the file
                using (Stream outstream = zipStream.AsStreamForWrite())
                {
                    byte[] buffer = stream.ToArray();
                    outstream.Write(buffer, 0, buffer.Length);
                    outstream.Flush();
                }
            }
            //Launch the saved Excel file.
            await Windows.System.Launcher.LaunchFileAsync(stFile);
        }
    }
}

The following screenshot illustrates the RowHeader displayed in WinUI DataGrid (SfDataGrid),

The following screenshot illustrates exported Excel Sheet with RowHeader,

Take a moment to peruse the WinUI DataGrid - Export To Excel documentation, where you can find about export to Excel with code examples.