Add support for TEXT function. The TEXT function allows changing the way a number appears by applying formatting to it using format codes.

TEXT(value, format_text)

A list of the supported functions is available at http://docs.telerik.com/devtools/document-processing/libraries/radspreadprocessing/features/formulas/functions 

This function can be implemented as a custom function. Check the following resources for more details on how to achieve that:

- http://docs.telerik.com/devtools/document-processing/libraries/radspreadprocessing/features/formulas/custom-functions 
- https://github.com/telerik/xaml-sdk/tree/master/Spreadsheet/WPF/CustomFunctions 

The r attribute of a cell defines the reference the cell is pointing to in a style similar to A1. Setting this attribute is optional but when set to an empty string, it cannot be imported - an ArgumentException is thrown with message "cellName" by the Guard class in NameConverter.ConvertCellNameToIndex().

Here is an example of such a definition:

<row r="1" spans="1:12">
  <c r=""/>
</row>


MS Excel and Libre Office can open such documents.

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".

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. 

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.

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();

Exporting empty workbook without any worksheet is not allowed according to the specification and such documents cannot be opened in Excel. Ensure the customers cannot create such documents using the API of SpreadProcessing.

Currently, the worksheet of the shape and the collection it belongs to should be the same. Make it possible for the ChartShape and the data source to be on different worksheets.

Adding a formula with the SetValueAsFormula method is slow

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

When a row or column is inserted in a worksheet that has cells referred from another worksheet, the formula should be updated so it refers to the same values as before the insertion or removal of cells.

Currently, the calculation of the actual ScaleFactor is based only on Worksheet`s UsedCellRange.

According to the Open XML documentation, the possible max value for this attribute is an unsignedInt or 4294967295.

Exporting a sheet in a workbook, results in clearly narrower column widths, this doesn't appear to be a scaling issue as letters that extend outside of a cell are occluded differently from the Excel document. Also worth noting, borders adjacent to the margin area are clipped (not an issue when exporting the same PDF from excel), text padding in the cell is not the same as the Excel document, and borders disappear unexpectedly on some text cells 

The Open Document Format for Office Applications (ODF), also known as OpenDocument, is an open standard file format for spreadsheets, charts, presentations, and word processing documents using ZIP-compressed[6] XML files.

The most common filename extension for spreadsheets is .ods.

The AutoFitWidth functionality does not take into account the filtering button.

The named ranges are not updated after rows or columns are inserted.

Introduce support for the WEEKDAY function.

Implement NewLine property in the CsvSettings class.

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: