@using Telerik.Windows.Documents.Spreadsheet.FormatProviders
@using Telerik.Windows.Documents.Spreadsheet.FormatProviders.OpenXml.Xlsx
@using Telerik.Windows.Documents.Spreadsheet.FormatProviders.TextBased.Csv
@using Telerik.Windows.Documents.Spreadsheet.Model

<TelerikGrid Data="@GridData" Pageable="true">
    <GridToolBarTemplate>
        <GridCommandButton Command="ExcelExport" Icon="@FontIcon.FileExcel">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" />
    </GridExport>

    <GridColumns>
        <GridColumn Field="@nameof(SampleData.ProductId)" Title="ID" Width="100px" />
        <GridColumn Field="@nameof(SampleData.ProductName)" Title="Product Name" Width="300px" />
        <GridColumn Field="@nameof(SampleData.UnitsInStock)" Title="In stock" Width="100px" />
        <GridColumn Field="@nameof(SampleData.Price)" Title="Unit Price" Width="200px" />
        <GridColumn Field="@nameof(SampleData.Discontinued)" Title="Discontinued" Width="100px" />
        <GridColumn Field="@nameof(SampleData.FirstReleaseDate)" Title="Release Date" Width="300px" />
    </GridColumns>
</TelerikGrid>

@code {
    private async Task OnExcelAfterExport(GridAfterExcelExportEventArgs args)
    {
        //args.Stream is finalized. The Import() method of the XlsxFormatProvider requires a readable stream, so you should copy the stream bytes to a new MemoryStream instance which will be used for the import.
        var bytes = args.Stream.ToArray();

        var excelStream = new MemoryStream(bytes);

        //create a format provider instance to call the import
        XlsxFormatProvider formatProvider = new XlsxFormatProvider();

        //import the stream to a workbook
        Workbook workbook = formatProvider.Import(excelStream);

        //loop through the cells
        CellRange usedCellRange = workbook.Worksheets[0].UsedCellRange;

        for (int rowIndex = usedCellRange.FromIndex.RowIndex; rowIndex <= usedCellRange.ToIndex.RowIndex; rowIndex++)
        {
            for (int columnIndex = usedCellRange.FromIndex.ColumnIndex; columnIndex <= usedCellRange.ToIndex.ColumnIndex; columnIndex++)
            {
                CellSelection cell = workbook.Worksheets[0].Cells[rowIndex, columnIndex];

                //get the cell value
                RangePropertyValue<ICellValue> rangeValue = cell.GetValue();
                ICellValue value = rangeValue.Value;

                //if the value length is 0, clear it
                if (value.RawValue.Length == 0)
                {
                    cell.ClearValue();
                }
            }
        }

        //save the modified workbook in a MemoryStream
        MemoryStream modifiedExport = new MemoryStream();

        formatProvider.Export(workbook, modifiedExport);

        //pass the modified stream to the event arguments
        args.Stream = modifiedExport;
    }

    List<SampleData> GridData { get; set; }

    bool ExportAllPages { get; set; }

    protected override void OnInitialized()
    {
        GridData = Enumerable.Range(1, 100).Select(x => new SampleData
            {
                ProductId = x,
                ProductName = $"Product {x}",
                UnitsInStock = x % 4 == 0? null : x * 2,
                Price = 3.14159m * x,
                Discontinued = x % 4 == 0,
                FirstReleaseDate = DateTime.Now.AddDays(-x)
            }).ToList();
    }

    public class SampleData
    {
        public int ProductId { get; set; }
        public string ProductName { get; set; }
        public int? UnitsInStock { get; set; }
        public decimal Price { get; set; }
        public bool Discontinued { get; set; }
        public DateTime FirstReleaseDate { get; set; }
    }
}