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).