If I simply import the xls file with the XlsFormatProvider that RadSpreadProcessing offers and then export it either to xls or xlsx format, the following message pops up when opening the document in MS Excel:
The exported XLS or XLSX file with RadSpreadProcessing contains an additional <definedName>:
<?xml version="1.0" encoding="utf-8"?>
<workbook xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships" xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main">
<sheets>
<sheet sheetId="1" name="Sheet1" state="visible" r:id="rId1" />
</sheets>
<definedNames>
<definedName name="Print_Titles" localSheetId="0" hidden="false">Sheet1!$A$1:$IV$3</definedName>
<definedName name="_xlnm.Print_Area" localSheetId="0" hidden="false">Sheet1!$A:$G</definedName>
<definedName name="_xlnm.Print_Titles" localSheetId="0" hidden="false">Sheet1!$1:$3</definedName>
</definedNames>
</workbook>