ClosedXML[
^] would be a better option for formatting
refer this to customize your need
ClosedXML - The easy way to OpenXML - Documentation[
^]
ClosedXML - styles[
^]
eg:
using (XLWorkbook wb = new XLWorkbook())
{
string fileName = "a.xlsx";
DataTable dt = new DataTable();
dt.Columns.Add("ID");
dt.Columns.Add("Name");
wb.Worksheets.Add(dt);
var sheet = wb.Worksheet(0);
sheet.Rows(1, 2).Style.Fill.BackgroundColor = XLColor.Blue;
sheet.Rows(1, 2).Style.Font.Bold = true;
sheet.Style.Font.FontSize = 9;
sheet.Style.Font.FontName = "calibiri";
}