Convert between German GAEB files and Austrian ÖNorm 2063 with the libraries by Dangl IT GmbH, see https://www.dangl-it.com/articles/convert-between-oenorm-2063-and-gaeb-files-with-danglava-dangloenorm-and-danglgaeb/

ExportToOenorm.cs

private async Task TransformToOenormAsync()
{
    var convertedProject = Dangl.Oenorm.Converter.ConvertToOenorm(_readProject, OenormDestinationType.LV2015);
    using (var oenormStream = Dangl.Oenorm.Writer.OenormWriter.GetStream(convertedProject))
    {
        var outputPath = Path.GetFullPath(_options.OutputFilePath);
        using (var fileStream = File.Create(outputPath))
        {
            await oenormStream.CopyToAsync(fileStream);
        }
    }
}

ImportGaeb.cs

private void ReadInputGaebFile()
{
    var filePath = Path.GetFullPath(_options.InputFilePath);
    using (var fileStream = File.OpenRead(filePath))
    {
        var gaebFile = Dangl.GAEB.Reader.GAEBReader.ReadGaeb(fileStream);
        _readProject = Dangl.AVA.Converter.Converter.ConvertFromGaeb(gaebFile);
    }
}