Note

Supports ClosedXML versions 0.96.0 and later, except for 0.103.x and 0.104.x due to thenot strongly named issue.

Using ClosedXML.Extension.EmbeddedObject:

public void AddTxtOleObject(){    var outputTargetPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Desktop), "AddTxtOleObject.xlsx");    var targetOleContentFilePath = Template.Sample("sample.txt");    var workbook = new XLWorkbook();    var helloOleWorksheet = workbook.Worksheets.Add("sampleTxt");    // 1. Load Object Sote    var helloOleWorksheetEmbeddedObjectStroe = helloOleWorksheet.GetEmbeddedObjectStore();    // 2. Record the information of the object to be embedded in Store    helloOleWorksheetEmbeddedObjectStroe.Add(new EmbeddedObjectInfo    {        OleObject = new StreamOleObjectInfo(new FileStream(targetOleContentFilePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite), targetOleContentFilePath),        Icon = IconSet.Txt.GetIconInfo(),        Dimension = DimensionInfo.FromCell(helloOleWorksheet.Cell($"A1"))    });    // 3. Write the embedded object when saving the workbook    workbook.SaveAsWithEmbeddedObjectGenerate(outputTargetPath);}

public class StreamOleObjectInfo : IOleObjectInfo{    public string FileName { get; private init; }    public string FilePath { get; private init; }    public string TemporaryPath { get; private init; }    private readonly Stream stream;    public StreamOleObjectInfo(Stream stream, string filePath, string fileName = null)    {        this.stream = stream;        this.FilePath = filePath;        this.FileName = fileName;        if (this.FileName == null)        {            var sourceFilePurePath = PathLib.PurePath.Create(filePath);            this.FileName = sourceFilePurePath.Filename;        }        this.TemporaryPath = this.FileName;    }    public bool IsContentStreamValid()    {        if(this.stream == null || this.stream.Length == 0) return false;        return true;    }    public Stream ContentStreamGetter()    {        this.stream.Position = 0;        return this.stream;    }}

// Default supported rendering methodsDimensionInfo.FromCell(helloOleWorksheet.Cell($"A1"))DimensionInfo.FromCellCenter(helloOleWorksheet.Cell($"A3"))DimensionInfo.FromRange( helloOleWorksheet.Range($"A5", $"A7"))public class XLRangeDimensionInfo : IDimensionInfo{    public IXLRange TargetRange { get; private init; }    public XLRangeDimensionInfo(IXLRange range)    {        if (range == null) throw new ArgumentNullException(nameof(range));        this.TargetRange = range;        var firstCell = this.TargetRange.FirstCell();        this.Column = firstCell.Address.ColumnNumber - 1;   // 1 Base TO 0 Base        this.Row = firstCell.Address.RowNumber - 1; // 1 Base TO 0 Base        var lastCell = this.TargetRange.LastCell();        this.ColumnCountWidth = lastCell.Address.ColumnNumber - firstCell.Address.ColumnNumber + 1;        this.RowCountHeight = lastCell.Address.RowNumber - firstCell.Address.RowNumber + 1;    }    public int Column { get; private init; }    public int Row { get; private init; }    public int ColumnCountWidth { get; private init; }    public int RowCountHeight { get; private init; }    public long ColumnFromOffset => 0;    public long ColumnToOffset => 0;}

new EmbeddedObjectInfo.IconInfo{    ImageContentType = "image/x-emf",    ImageStreamGetter = getEmbeddedResourceIcon("text.emf")};private static Stream getEmbeddedResourceIcon(string fileName){    return _assembly.Value.GetManifestResourceStream($"{_namespace.Value}.{fileName}");}