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

XIRR function returns the internal rate of return for a schedule of cash flows that is not necessarily periodic. To calculate the internal rate of return for a series of periodic cash flows, use the IRR function.

https://support.microsoft.com/en-gb/office/xirr-function-de1242ec-6477-445b-b11b-a303ad9adc9d 

Import an XLSX document and auto-fit the columns. Then, export the document to XLSX format.

Even though a SpreadFixedTextMeasurer is applied and a FontProvider is implemented, the columns are not wide enough to fit the content:

Incorrectly resolved fill between local formatting and cell style.

A fill (fillId) of a cell style (cellStyleXfs) is respected instead of the fill (fillId) of the local formatting (cellXfs).