Custom Cell Formatting of the Exported File with RadSpreadStreamProcessing

@using System.IO
@using Telerik.Documents.SpreadsheetStreaming

<TelerikGrid Data="@GridData"
             Pageable="true">
    <GridToolBarTemplate>
        <GridCommandButton Command="ExcelExport">Export to Excel</GridCommandButton>
        <label class="k-checkbox-label">
            <TelerikCheckBox @bind-Value="@ExportAllPages" />
            Export All Pages
        </label>
    </GridToolBarTemplate>

    <GridExport>
        <GridExcelExport FileName="telerik-grid-export"
                         AllPages="@ExportAllPages"
                         OnAfterExport="@OnExcelAfterExport">
        </GridExcelExport>
    </GridExport>

    <GridColumns>
        <GridColumn Field="@nameof(Product.Id)" Title="ID" Width="60px" />
        <GridColumn Field="@nameof(Product.Name)" Title="Product Name" Width="180px" />
        <GridColumn Field="@nameof(Product.Price)" Width="160px" />
        <GridColumn Field="@nameof(Product.Quantity)" Width="120px" />
        <GridColumn Field="@nameof(Product.ReleaseDate)" Title="Release Date" DisplayFormat="{0:d}" Width="240px" />
        <GridColumn Field="@nameof(Product.Discontinued)" Width="160px" />
    </GridColumns>
</TelerikGrid>

@code {
    private List<Product> GridData { get; set; } = new();

    private bool ExportAllPages { get; set; }

    private void OnExcelAfterExport(GridAfterExcelExportEventArgs args)
    {
        byte[] bytes = args.Stream.ToArray();

        using MemoryStream importStream = new MemoryStream(bytes);

        using MemoryStream exportStream = new MemoryStream();

        // Define the desired styling.
        // https://docs.telerik.com/devtools/document-processing/libraries/radspreadstreamprocessing/features/cell-styles
        SpreadCellFormat customCellFormat = new SpreadCellFormat()
        {
            Fill = SpreadPatternFill.CreateSolidFill(new SpreadColor(230, 238, 223)),
            IsBold = true
        };

        // Import the stream to modify it and then export it.
        // https://docs.telerik.com/devtools/document-processing/libraries/radspreadstreamprocessing/model/workbook
        using IWorkbookImporter workBookImporter = SpreadImporter.CreateWorkbookImporter(SpreadDocumentFormat.Xlsx, importStream);

        using IWorkbookExporter workbookExporter = SpreadExporter.CreateWorkbookExporter(SpreadDocumentFormat.Xlsx, exportStream);

        // Loop through the sheets to copy their content.
        foreach (IWorksheetImporter worksheetImporter in workBookImporter.WorksheetImporters)
        {
            using IWorksheetExporter worksheetExporter = workbookExporter.CreateWorksheetExporter(worksheetImporter.Name);

            // Set fixed width to all columns.
            // If you need to autofit the content, use the CellContentSizeHelper:
            //https://docs.telerik.com/devtools/document-processing/libraries/radspreadstreamprocessing/features/text-measuring
            for (int i = 0; i < 6; i++)
            {
                IColumnExporter column = worksheetExporter.CreateColumnExporter();

                column.SetWidthInPixels(160);

                column.Dispose();
            }

            int lastRow = 0;

            // Loop through the rows to copy their content.
            foreach (IRowImporter rowImporter in worksheetImporter.Rows)
            {
                int rowDifference = rowImporter.RowIndex - lastRow;

                // Ensure proper row order in case there are any empty rows.
                if (rowDifference > 1)
                {
                    worksheetExporter.SkipRows(rowDifference - 1);
                }

                int lastColumn = 0;

                using IRowExporter rowExporter = worksheetExporter.CreateRowExporter();

                // Loop through the cells to copy their content.
                foreach (ICellImporter cellImporter in rowImporter.Cells)
                {
                    string value = cellImporter.Value;

                    if (string.IsNullOrEmpty(value))
                    {
                        continue;
                    }

                    CellValueType valueType = cellImporter.ValueType;

                    SpreadCellFormat importedFormat = new SpreadCellFormat();

                    if (cellImporter.Format != null)
                    {
                        importedFormat = cellImporter.Format;
                    }

                    int cellDifference = cellImporter.ColumnIndex - lastColumn;

                    // Ensure proper cell order in case there are any empty cells.
                    if (cellDifference > 1)
                    {
                        rowExporter.SkipCells(cellDifference - 1);
                    }

                    // Check the cell value to apply proper formatting.
                    using ICellExporter cellExporter = rowExporter.CreateCellExporter();

                    switch (valueType)
                    {
                        case CellValueType.Boolean:
                            bool boolValue = bool.Parse(value);
                            cellExporter.SetValue(boolValue);
                            break;
                        case CellValueType.Number:
                            double dateNumberValue = double.Parse(value);
                            cellExporter.SetFormat(importedFormat);
                            cellExporter.SetValue(dateNumberValue);
                            break;
                        case CellValueType.Error:
                        case CellValueType.Text:
                        case CellValueType.SharedString:
                        case CellValueType.RichText:
                            cellExporter.SetValue(value);
                            break;
                    }

                    // Apply the defined style to the desired cells.
                    if (cellImporter.RowIndex == 0)
                    {
                        cellExporter.SetFormat(customCellFormat);
                    }

                    lastColumn = cellImporter.ColumnIndex;
                }

                lastRow = rowImporter.RowIndex;
            }
        }

        // Pass the modified stream to the GridAfterExcelExportEventArgs event argument.
        args.Stream = exportStream;
    }

    protected override void OnInitialized()
    {
        Random rnd = Random.Shared;
        GridData = Enumerable.Range(1, 100).Select(x => new Product
        {
            Id = x,
            Name = $"Product {x}",
            Price = rnd.Next(1, 100) * 1.23m,
            Quantity = rnd.Next(0, 100),
            ReleaseDate = DateTime.Now.AddDays(-rnd.Next(1, 1000)),
            Discontinued = x % 4 == 0
        }).ToList();
    }

    public class Product
    {
        public int Id { get; set; }
        public string Name { get; set; } = string.Empty;
        public decimal Price { get; set; }
        public int Quantity { get; set; }
        public DateTime ReleaseDate { get; set; }
        public bool Discontinued { get; set; }
    }
}