Applying text format to a column also sets the format to the next column.

This happens when the columns have a size different from the default and two consecutive columns with different format also have the same size. This can be worked around with a slight change in the column sizes:

int columnCount = worksheet.UsedCellRange.ColumnCount;

for(int i = 1; i < columnCount; i++)
{
    ColumnWidth colWidth = worksheet.Columns[i].GetWidth().Value;
    if(colWidth.Value != SpreadsheetDefaultValues.DefaultColumnWidth)
    {
        ColumnWidth previousColWidth = worksheet.Columns[i - 1].GetWidth().Value;

        if(colWidth.Equals(previousColWidth))
        {
            worksheet.Columns[i].SetWidth(new ColumnWidth(colWidth.Value + 1, colWidth.IsCustom));
        }
    }
}

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.