BigExcelCreator 3.4.2026.10623

Big Excel Creator

Create Excel files using OpenXML SAX with styling. This is specially useful when trying to output thousands of rows.

The idea behind this package is to be a basic easy-to-use wrapper around a reduced subset of functions of DocumentFormat.OpenXml aimed towards generating large excel files as fast as possible using the SAX method for writing.

At the same time, this writer should prevent you from creating an invalid file (i.e.: a file generated without any errors, but unable to be opened). Since the most common reason for a file to become corrupted when creating it using SAX is out-of-order instructions (i.e.: writing to a cell outside a sheet), this package should detect that, and throw an exception.

NOTE

Version 2.x of this package is linked to version 2.20.0 of DocumentFormat.OpenXml, and starting on version 3, BigExcelCreator is linked to version 3 of DocumentFormat.OpenXml.

Version 2.3.x is maintained as legacy. New features might be included, but not guaranteed. Testing is limited. I recommend using version 3.x if possible.

If you're already using DocumentFormat.OpenXml v2, either directly or as transitive reference, and you can't upgrade for some reason (e.g. dependency on another package), use BigExcelCreator v2

Otherwise, I recommend using the latest version available.

Table of Contents

• Usage
  • Shared Strings
  • Creating sheets from objects
• Data Validation
• Styling and formatting
  • Column formatting
  • Hide Sheet
  • Merge Cells
  • Styling
  • Comments
  • Autofilter
  • Conditional Formatting
    • Formula
    • Cell Is
    • Duplicated Values
• Page Layout
  • Sheet options
    • Gridlines
    • Headings

Usage

To see a working example, see the example code on gitHub, part of the vs solution.

1. Instantiate class BigExcelWriter using either a file path or a stream (MemoryStream is recommended).

2. Open a new Sheet using CreateAndOpenSheet

3. For every row, use BeginRow and EndRow

   • If you want to hide a row, pass true when calling BeginRow

4. Between BeginRow and EndRow, use WriteTextCell to write a cell.

   Alternatively, you can use WriteTextRow to write an entire row at once, using the same format.

   Text cells can be written using the shared strings table, which can reduce the generated file size. See Shared Strings below.

   If you are exporting a collection of objects, use CreateSheetFromObject. See Creating sheets from objects for object-based export and configuration.

   See more in the example code and in the API documentation

5. Use WriteFormulaCell or WriteFormulaRow to insert formulas.

6. Use WriteNumberCell or WriteNumberRow to insert numbers. This is useful if you need to do any calculation later on.

7. Use CloseSheet to finish.

8. If needed, repeat steps 2 → 5 to write to another sheet

Shared Strings

If the same text appears across different sheets, using the shared strings table may help reduce the generated file size. In order to do this, simply set to true the useSharedStrings parameter when calling WriteTextCell or WriteTextRow.

If you use object export with CreateSheetFromObject, enable useSharedStringsOnTextData for the same shared-string optimization. See Creating sheets from objects.

Creating sheets from objects

Use CreateSheetFromObject to write an entire sheet from a collection of objects. This method maps object properties to sheet columns and applies attribute-based configuration for headers, styles, and conditional formatting.

using BigExcelCreator;
using BigExcelCreator.ClassAttributes;

[ExcelHeaderStyleFormat("HeaderStyle")]
public class Product
{
    [ExcelColumnOrder(0)]
    [ExcelColumnName("Product Id")]
    [ExcelColumnType(CellDataType.Number)]
    [ExcelColumnWidth(10)]
    public int Id { get; set; }

    [ExcelColumnOrder(1)]
    [ExcelColumnName("Product Name")]
    [ExcelColumnType(CellDataType.Text)]
    [ExcelColumnWidth(25)]
    public string Name { get; set; } = string.Empty;
}

....

MemoryStream stream = new MemoryStream();
using (BigExcelWriter excel = new(stream))
{
    var data = new List<Product>
    {
        new() { Id = 1, Name = "Product A" },
        new() { Id = 2, Name = "Product B" }
    };
    
    excel.CreateSheetFromObject(data, "Products");
    excel.CloseSheet();
}

Available attributes for configuration:

• ExcelIgnore: Exclude property from output
• ExcelColumnName: Custom column header
• ExcelColumnOrder: Column position (0-based)
• ExcelColumnType: Cell data type mapping
• ExcelColumnWidth: Column width in characters
• ExcelColumnHidden: Hide column from view
• ExcelStyleFormat: Style for data cells
• ExcelHeaderStyleFormat: Style for header row
• ExcelConditionalFormatFormula: Formula-based conditional formatting
• ExcelConditionalFormatCellIs: Value-based conditional formatting
• ExcelConditionalFormatDuplicatedValues: Highlight duplicates

See the API documentation for more details.

Example

using BigExcelCreator;

....

MemoryStream stream = new MemoryStream();
using (BigExcelWriter excel = new(stream))
{
    excel.CreateAndOpenSheet("Sheet Name");
    excel.BeginRow();
    excel.WriteTextCell("Cell content");
    excel.WriteTextCell(123); // write as number. This allows to use formulas.
    excel.WriteTextCell(456);
    excel.WriteFormulaCell("SUM(B1:C1)");
    excel.EndRow();
    excel.BeginRow(true);
    excel.WriteTextCell("This row is hidden");
    excel.EndRow();
    excel.CloseSheet();
}

Data Validation

Use AddListValidator to restrict, to a list defined in a formula, possible values to be written to a cell by an user.

If you are exporting objects with CreateSheetFromObject, use conditional formatting attributes on properties instead of per-cell validation. See Creating sheets from objects.

Alternatively, use AddIntegerValidator or AddDecimalValidator to restrict / validate values as defined by validationType (equal, greater than, between, etc.)

    excel.CreateAndOpenSheet("Sheet Name");
    
    ...    
    
    // Only allow values included in sheet named "vals" between cells A1 and A6
    // when writing to cells between B2 and B10 of the current sheet.
    string range = "B2:B10";
    string formula = "vals!$A$1:$A$6";
    excel.AddValidator(range, formula);
    
    excel.CloseSheet();

Styling and formatting

Column formatting

When calling CreateAndOpenSheet, pass IList<Column> as second parameter. Each element represents a single column. Only the CustomWidth, Width and Hidden are used.

When using CreateSheetFromObject, styling and conditional formatting can be configured on object properties using attributes. See Creating sheets from objects.

Width represents the column width in characters (Same unit as when resizing in Excel).

CustomWidth allows the use of Width.

Hidden hides the column.

Example

List<Column> cols = new List<Column> {
    new Column{CustomWidth = true, Width=10},   // A
    new Column{CustomWidth = true, Width=15},   // B
    new Column{CustomWidth = true, Width=18},   // c
};

excel.CreateAndOpenSheet("Sheet Name", cols);

Hide Sheet

CreateAndOpenSheet accepts as third parameter a SheetStateValues variable.

• SheetStateValues.Visible (default): Sheet is visible
• SheetStateValues.Hidden: Sheet is hidden
• SheetStateValues.VeryHidden: Sheet is hidden and cannot be unhidden from Excel's UI.

When exporting collections with CreateSheetFromObject, you can also control sheet visibility using the same SheetStateValues parameter. See Creating sheets from objects.

Merge Cells

In order to merge a range of cells while a sheet is open, use MergeCells with a range.

excel.MergeCells("A1:A5");

Styling

First, the elements that define a style (font, fill, border and, optionally, numbering format) must be created.

font1 = new Font(new Bold(),
            new FontSize { Val = 11 },
            new Color { Rgb = new HexBinaryValue { Value = "000000" } },
            new FontName { Val = "Calibri" });

fill1 = new Fill(
            new PatternFill { PatternType = PatternValues.Gray125 });
fill2 = new Fill(
            new PatternFill (
                new ForegroundColor { Rgb = new HexBinaryValue { Value = "FFFF00" } }
            )
            { PatternType = PatternValues.Solid });

border1 = new Border(
            new LeftBorder(
                new Color { Rgb = new HexBinaryValue { Value = "FFD3D3D3" } }
            )
            { Style = BorderStyleValues.Thin },
            new RightBorder(
                new Color { Rgb = new HexBinaryValue { Value = "FFD3D3D3" } }
            )
            { Style = BorderStyleValues.Thin },
            new TopBorder(
                new Color { Rgb = new HexBinaryValue { Value = "FFD3D3D3" } }
            )
            { Style = BorderStyleValues.Thin },
            new BottomBorder(
                new Color { Rgb = new HexBinaryValue { Value = "FFD3D3D3" } }
            )
            { Style = BorderStyleValues.Thin },
            new DiagonalBorder());

numberingFormat1 = new NumberingFormat { NumberFormatId = 164, FormatCode = "0,.00;(0,.00)" };

After that, a new style list can be created and new styles inserted. Remember to name you styles.

StyleList list = new StyleList();
string name1 = "name1";
string name2 = "name2";

list.NewStyle(font1, fill1, border1, numberingFormat1, name1);
list.NewStyle(font1, fill2, border1, numberingFormat1, name2);

When instantiating BigExcelWriter, use the result of calling GetStylesheet as the stylesheet parameter. Then, when writing a cell, you can use the name given earlier to format it.

MemoryStream stream = new MemoryStream();
using (BigExcelWriter excel = new(stream,
                                    DocumentFormat.OpenXml.SpreadsheetDocumentType.Workbook
                                    stylesheet: list.GetStylesheet()))
{
    int index_style_name1 = list.GetIndexByName(name1);
    int index_style_name2 = list.GetIndexByName(name2);
    excel.CreateAndOpenSheet("Sheet Name");
    excel.BeginRow();
    excel.WriteTextCell("This has a gray patterned background", index_style_name1);
    excel.WriteTextCell("This has a yellow background", index_style_name2);
    excel.EndRow();
    excel.CloseSheet();
}

If you're planning to use Conditional Formatting, you must also create differential styles here. To do so, follow the same instructions as above, replacing NewStyle with NewDifferentialStyle.

All parameters of NewDifferentialStyle are optional, except name. Of the optional parameters, at least one must be present.

// place this before calling list.GetStylesheet() and new BigExcelWriter()
list.NewDifferentialStyle("RED", font: new Font(new Color { Rgb = new HexBinaryValue { Value = "FF0000" } }));

Comments

In order to add a note (formerly known as comment) to a cell, while a sheet is open, call the Comment method.

excel.CreateAndOpenSheet("Sheet Name");
excel.BeginRow();

excel.WriteTextCell("This has a gray patterned background", index_style_name1);
excel.WriteTextCell("This has a yellow background", index_style_name2);

excel.Comment("test A1 another sheet", "A1");

excel.EndRow();

excel.Comment("test E2 another sheet", "B1", "Author");

excel.CloseSheet();

Autofilter

In order to add an Autofilter, call AddAutofilter while on a sheet.

excel.BeginRow();
// ...
excel.AddAutofilter(range); // Range's height must be 1. Example: A1:J1
// ...
excel.EndRow();

Conditional Formatting

In order to use conditional formatting, you should define Differential styles (see Styling)

On every case below:

• reference ⇒ A range of cells to apply the conditional formatting to
• format ⇒ The id of the Differential style. Obtain it using GetIndexDifferentialByName after creating it with NewDifferentialStyle

Formula

To define a conditional style by formula, use AddConditionalFormattingFormula(string reference, string formula, int format).

• formula defines the expression to use. Use a fixed range using $ to anchor the reference to a cell. Avoid using $ to make the reference "walk" with the range. This is useful when referencing the current cell.

excel.AddConditionalFormattingFormula("A1:A10", "A1<5", styleList.GetIndexDifferentialByName("RED"));

Cell Is

Format cells based on their contents using AddConditionalFormattingCellIs

• Operator defines how to compare values.
• value defines the value to compare the cell to.
• value2 If the operator requires 2 numbers (eg: Between and NotBetween), the second value goes here.

excel.AddConditionalFormattingCellIs("A1:A20", ConditionalFormattingOperatorValues.LessThan, "5", styleList.GetIndexDifferentialByName("RED"));
excel.AddConditionalFormattingCellIs("A1:A20", ConditionalFormattingOperatorValues.Between, "3", styleList.GetIndexDifferentialByName("RED"), "7");

Duplicated Values

Format duplicated values using AddConditionalFormattingDuplicatedValues

excel.AddConditionalFormattingDuplicatedValues("A1:A10", styleList.GetIndexDifferentialByName("RED"));

Page Layout

Sheet options

Gridlines

While working on a sheet, the property ShowGridLinesInCurrentSheet controls whether the gridlines are shown. Enabled by default.

While working on a sheet, the property PrintGridLinesInCurrentSheet controls whether the gridlines are printed. Disabled by default.

Headings

While working on a sheet, the property ShowRowAndColumnHeadingsInCurrentSheet controls whether the headings (Column letters and row numbers) are shown. Enabled by default.

While working on a sheet, the property PrintRowAndColumnHeadingsInCurrentSheet controls whether the headings (Column letters and row numbers) are printed. Disabled by default.