Excel Newline or Hard Return

Yes, you can include newlines (hard returns) in Excel cell values—including column headers—when generating Excel files with OpenXML or ClosedXML.

✅ With ClosedXML

You can insert a newline in a string using Environment.NewLine (or "\n"), and enable text wrapping:

var worksheet = workbook.Worksheets.Add("Sheet1");
worksheet.Cell("A1").Value = "PROGRAM" + Environment.NewLine + "_NUM";
worksheet.Cell("A1").Style.Alignment.WrapText = true;

📌 Tip: Environment.NewLine is platform-safe, but Excel also handles just "\n" fine.

✅ With OpenXML SDK

You must set the cell's value with a Text element that has xml:space="preserve" and use "\n" for the line break. You also need to enable text wrapping via cell style.

Example:

var cell = new Cell
{
    DataType = CellValues.InlineString,
    InlineString = new InlineString
    {
        Text = new Text { Text = "PROGRAM\n_NUM", Space = SpaceProcessingModeValues.Preserve }
    }
};

Then apply a CellFormat that sets ApplyAlignment = true and Alignment.WrapText = true.

📝 Excel Output

This will visually show as:

PROGRAM
_NUM

in the same cell.

Would you like a working sample for either OpenXML or ClosedXML?

Here are working samples for both ClosedXML and OpenXML SDK to generate an Excel file with a column header containing a newline (PROGRAM\n_NUM):

✅ ClosedXML Sample

using ClosedXML.Excel;

// Create a new workbook and worksheet
using var workbook = new XLWorkbook();
var worksheet = workbook.Worksheets.Add("Sample");

// Add a header with a newline
worksheet.Cell("A1").Value = "PROGRAM\n_NUM";

// Enable wrap text
worksheet.Cell("A1").Style.Alignment.WrapText = true;

// Optionally, auto-adjust row height and column width
worksheet.Columns().AdjustToContents();
worksheet.Rows().AdjustToContents();

// Save to file
workbook.SaveAs("closedxml_newline_header.xlsx");

📝 The \n works fine, but you can also use Environment.NewLine.

✅ OpenXML SDK Sample

This example uses OpenXML SDK DocumentFormat.OpenXml to do the same. You'll need to add the DocumentFormat.OpenXml NuGet package.

using DocumentFormat.OpenXml;
using DocumentFormat.OpenXml.Packaging;
using DocumentFormat.OpenXml.Spreadsheet;

using var spreadsheet = SpreadsheetDocument.Create("openxml_newline_header.xlsx", SpreadsheetDocumentType.Workbook);

// Add workbook and worksheet parts
var workbookPart = spreadsheet.AddWorkbookPart();
workbookPart.Workbook = new Workbook();
var worksheetPart = workbookPart.AddNewPart<WorksheetPart>();

// Add sheet data
var sheetData = new SheetData();
worksheetPart.Worksheet = new Worksheet(sheetData);

// Create row and cell
var row = new Row();
var cell = new Cell
{
    DataType = CellValues.InlineString,
    InlineString = new InlineString
    {
        Text = new Text
        {
            Text = "PROGRAM\n_NUM",
            Space = SpaceProcessingModeValues.Preserve
        }
    }
};
row.Append(cell);
sheetData.Append(row);

// Create stylesheet with wrap text
var stylesheetPart = workbookPart.AddNewPart<WorkbookStylesPart>();
stylesheetPart.Stylesheet = new Stylesheet(
    new Fonts(new Font()), // Default font
    new Fills(new Fill()), // Default fill
    new Borders(new Border()), // Default border
    new CellFormats(
        new CellFormat(), // Index 0 - default
        new CellFormat { ApplyAlignment = true, Alignment = new Alignment { WrapText = true } } // Index 1
    )
);
stylesheetPart.Stylesheet.Save();

// Apply style index 1 (wrap text)
cell.StyleIndex = 1;

// Add the sheet
var sheets = spreadsheet.WorkbookPart.Workbook.AppendChild(new Sheets());
sheets.Append(new Sheet
{
    Id = spreadsheet.WorkbookPart.GetIdOfPart(worksheetPart),
    SheetId = 1,
    Name = "Sheet1"
});

spreadsheet.WorkbookPart.Workbook.Save();

Let me know if you want this wrapped in a console app template or if you want to add more styling (like borders or background color).

Here’s a complete .NET 8 Console App for both ClosedXML and OpenXML examples. The app generates two Excel files with a newline in the header cell (PROGRAM\n_NUM):

🧾 Project Setup

Create a new .NET 8 console app:

dotnet new console -n ExcelHeaderNewlineDemo
cd ExcelHeaderNewlineDemo

Add required NuGet packages:

dotnet add package ClosedXML
dotnet add package DocumentFormat.OpenXml

✨ `Program.cs`

Replace the contents of Program.cs with:

using ClosedXML.Excel;
using DocumentFormat.OpenXml;
using DocumentFormat.OpenXml.Packaging;
using DocumentFormat.OpenXml.Spreadsheet;

CreateWithClosedXml();
CreateWithOpenXml();

Console.WriteLine("Excel files created successfully.");

// ---------- CLOSEDXML ----------
static void CreateWithClosedXml()
{
    using var workbook = new XLWorkbook();
    var worksheet = workbook.Worksheets.Add("ClosedXML");

    worksheet.Cell("A1").Value = "PROGRAM\n_NUM";
    worksheet.Cell("A1").Style.Alignment.WrapText = true;

    worksheet.Columns().AdjustToContents();
    worksheet.Rows().AdjustToContents();

    workbook.SaveAs("ClosedXml_HeaderNewline.xlsx");
}

// ---------- OPENXML SDK ----------
static void CreateWithOpenXml()
{
    using var spreadsheet = SpreadsheetDocument.Create("OpenXml_HeaderNewline.xlsx", SpreadsheetDocumentType.Workbook);

    var workbookPart = spreadsheet.AddWorkbookPart();
    workbookPart.Workbook = new Workbook();

    var worksheetPart = workbookPart.AddNewPart<WorksheetPart>();
    var sheetData = new SheetData();
    worksheetPart.Worksheet = new Worksheet(sheetData);

    // Define the row and cell
    var row = new Row();
    var cell = new Cell
    {
        DataType = CellValues.InlineString,
        InlineString = new InlineString
        {
            Text = new Text
            {
                Text = "PROGRAM\n_NUM",
                Space = SpaceProcessingModeValues.Preserve
            }
        },
        StyleIndex = 1
    };
    row.Append(cell);
    sheetData.Append(row);

    // Add styles with wrap text
    var stylesPart = workbookPart.AddNewPart<WorkbookStylesPart>();
    stylesPart.Stylesheet = new Stylesheet(
        new Fonts(new Font()), // Default font
        new Fills(new Fill()), // Default fill
        new Borders(new Border()), // Default border
        new CellFormats(
            new CellFormat(), // Index 0 - default
            new CellFormat
            {
                ApplyAlignment = true,
                Alignment = new Alignment { WrapText = true }
            }
        )
    );
    stylesPart.Stylesheet.Save();

    // Create Sheets collection
    var sheets = spreadsheet.WorkbookPart.Workbook.AppendChild(new Sheets());
    sheets.Append(new Sheet
    {
        Id = spreadsheet.WorkbookPart.GetIdOfPart(worksheetPart),
        SheetId = 1,
        Name = "OpenXML"
    });

    spreadsheet.WorkbookPart.Workbook.Save();
}

✅ To Run

dotnet run

It will create:

ClosedXml_HeaderNewline.xlsx
OpenXml_HeaderNewline.xlsx

with wrapped headers like:

PROGRAM
_NUM

Let me know if you'd like to package this or export it to other formats like .csv or .pdf.

stormwild/excel-hard-return.md