Excel And Datatable

You can do this way

using ClosedXML.Excel;
using System.Linq;

public class Main
{
    public static void HighlightEmptyRows(IXLWorksheet worksheet)
    {
        // Iterate through rows in the sheet.
        foreach (var row in worksheet.RowsUsed())
        {
            //Check if all cells are Empty.
            if (row.Cells().All(cell => cell.IsEmpty()))
            {
                // Then Mark Empty
                row.Style.Fill.BackgroundColor = XLColor.Red; 
            }
        }
    }
}