var newFile = @"newbook.core.xlsx";

using (var fs = new FileStream(newFile, FileMode.Create, FileAccess.Write)) {

    IWorkbook workbook = new XSSFWorkbook();

    ISheet sheet1 = workbook.CreateSheet("Sheet1");

    sheet1.AddMergedRegion(new CellRangeAddress(0, 0, 0, 10));
    var rowIndex = 0;
    IRow row = sheet1.CreateRow(rowIndex);
    row.Height = 30 * 80;
    row.CreateCell(0).SetCellValue("this is content, very long content, very long content, very long content, very long content");
    sheet1.AutoSizeColumn(0);
    rowIndex++;


    var sheet2 = workbook.CreateSheet("Sheet2");
    var style1 = workbook.CreateCellStyle();
    style1.FillForegroundColor = HSSFColor.Blue.Index2;
    style1.FillPattern = FillPattern.SolidForeground;

    var style2 = workbook.CreateCellStyle();
    style2.FillForegroundColor = HSSFColor.Yellow.Index2;
    style2.FillPattern = FillPattern.SolidForeground;

    var cell2 = sheet2.CreateRow(0).CreateCell(0);
    cell2.CellStyle = style1;
    cell2.SetCellValue(0);

    cell2 = sheet2.CreateRow(1).CreateCell(0);
    cell2.CellStyle = style2;
    cell2.SetCellValue(1);

    workbook.Write(fs);
}

var newFile2 = @"newbook.core.docx";
using (var fs = new FileStream(newFile2, FileMode.Create, FileAccess.Write)) {
    XWPFDocument doc = new XWPFDocument();
    var p0 = doc.CreateParagraph();
    p0.Alignment = ParagraphAlignment.CENTER;
    XWPFRun r0 = p0.CreateRun();
    r0.FontFamily = "microsoft yahei";
    r0.FontSize = 18;
    r0.IsBold = true;
    r0.SetText("This is title");

    var p1 = doc.CreateParagraph();
    p1.Alignment = ParagraphAlignment.LEFT;
    p1.IndentationFirstLine = 500;
    XWPFRun r1 = p1.CreateRun();
    r1.FontFamily = "·ÂËÎ";
    r1.FontSize = 12;
    r1.IsBold = true;
    r1.SetText("This is content, content content content content content content content content content");

    doc.Write(fs);
}