When a chart is created with RadSpreadProcessing, by default it is exported with legend showing category list. If an xlsx file with a chart with legend showing only series is imported and exported, it will be changed to category list as well. API to switch between the two should be added.

Legend showing category list:

Legend showing series:

When the column width is not an integer number, but a decimal fraction one, the width which is exported is not calculated correctly. 

For example, if there is a cell with some text and its column's width is autofit, it's exported with different actual width.

In addition, if the exported xlsx file is imported back in the Spreadsheet, the column width is a bit different from the one which was exported (only for the first export-import roundtrip).

Incorrect calculation of UsedCellRange when conditional formatting is applied to a large cell range.

Workaround:

var usedCellRange = workbook.ActiveWorksheet.GetUsedCellRange(
    CellPropertyDefinitions.AllPropertyDefinitions
    .Except(
        CellPropertyDefinitions.AllPropertyDefinitions.Where(p => p.Name == "DataValidationRule" || p.Name == "ConditionalFormatting")));

Currently, this could be achieved by exporting the document to PDF and then by using RadPdfViewer's WPF control ThumbnailFactory class. Sample code may be seen at this forum post: http://www.telerik.com/forums/pdf-thumbnail-returns-transparent-images#jO33X-E8Cki_qLh_KsToWg Help article: WPF PdfViewer - Exporting Fixed Page to Image - Telerik UI for WPF

In WorksheetPageSetup, you can only get the PageSize, but not set it. The only way is through setting a PaperType.

This is because in Telerik.Windows.Documents.Spreadsheet.Model.Printing.SheetPageSetupBase, the only way to set the pageSize property is by setting a PaperType, then it uses PaperTypeConverter.ToSize(PaperType) to convert it to the pageSize. I cannot see any other way to set this to a custom size set by the user.

Please allow custom page sizing by adding a setter for the PageSize if possible. Thank you!

WorksheetPageSetup pageSetup = worksheet.WorksheetPageSetup;
Size pageSize = new Size(50, 80)
pageSetup.PageSize = pageSize; // produces cs0200
pageSetup.PageSize.Width = pageSize.Width; // produces cs1612
pageSetup.PageSize.Height = pageSize.Height; // produces cs1612

Implement a GoalSeek functionality.

When inserting cells a check is performed for data loss. This check should take into account the value property, but should not take into account properties like cell value format and data validation. 

Workaround: clear the values at the end of the worksheet before inserting cells.
worksheet.Cells[1048575, 0, 1048575, 16383].ClearDataValidationRule();

When the scale factor of a document is smaller, the borders don't seem to scale correctly when exported to PDF. They appear much thicker than they would when exported from Excel.

The OFFSET function returns a reference to a range that is a specified number of rows and columns from a cell or range of cells. 

Having cell with custom format string set to "MMM" does not apply correctly. Instead of showing the date in the defined format (for instance "Aug"), what actually is displayed is "MMM".