If a rule is added with no formatting (for example, in the case when we want to add a rule which preserves the default formatting in some cases) the exported document is corrupted.

DifferentialFormatting formatting2 = new DifferentialFormatting();

ContainsBlanksRule rule2 = new ContainsBlanksRule(formatting2);
rule2.Formatting = formatting2;

ConditionalFormatting conditionalFormatting2 = new ConditionalFormatting(rule2);
worksheet.Cells[1, 2, 12, 2].AddConditionalFormatting(conditionalFormatting2);

DifferentialFormatting formatting2 = new DifferentialFormatting();
formatting2.Fill = new PatternFill(PatternType.Solid, Colors.Transparent, Colors.Transparent);
CellBorder border = new CellBorder(CellBorderStyle.Thin, new ThemableColor(Color.FromRgb(212, 212, 212)));
formatting2.LeftBorder = border;
formatting2.TopBorder = border;
formatting2.RightBorder = border;
formatting2.BottomBorder = border;

When an xlsm file is imported and then exported, a new ThisWorkbook object is created in the VBA browser. This creates issues when making VBA functions that have to be executed upon opening of the file.

When there are unclosed quotes (") several cells/rows are imported as one.

A possible workaround is to replace all the quote (") symbols with single quote (') symbols.

Sometimes leading minus sign in a cell with text is treated as a formula.

A possible workaround is to remove the minus sign or to replace it with some other symbol.

Use the code to import a sample txt file containing a "+" sign in a cell value:

 Workbook workbook;
 Telerik.Windows.Documents.Spreadsheet.FormatProviders.IWorkbookFormatProvider formatProvider = new Telerik.Windows.Documents.Spreadsheet.FormatProviders.TextBased.Txt.TxtFormatProvider();

 using (Stream input = new FileStream(@"sample.txt", FileMode.Open))
 {
     workbook = formatProvider.Import(input);
 }

Expected behavior: the file is imported successfully

Actual behavior: an error is thrown