Why office365 xlsx sheet utf8 encoding but openxmlsdk is utf8-withbom

[shps951023]

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Description

Please provide a simple description of the issue encountered.

Information

• .NET Target: .NET Core
• DocumentFormat.OpenXml Version: 2.14.0

Repro

public class Program
{
	public static void Main(string[] args)
	{
		var directoryInfo = new DirectoryInfo(Directory.GetCurrentDirectory());
		var fileName = $@"PracticePart1-{DateTime.Now:yyyyMMddHHmmss}.xlsx";
		var filepath = Path.Combine(directoryInfo.ToString(), fileName);
		Console.WriteLine($"FilePath: {filepath}");
		var spreadsheetDocument = SpreadsheetDocument.Create(filepath, SpreadsheetDocumentType.Workbook);
		var workbookPart = spreadsheetDocument.AddWorkbookPart();
		workbookPart.Workbook = new Workbook();
		var worksheetPart = workbookPart.AddNewPart<WorksheetPart>();
		worksheetPart.Worksheet = new Worksheet(new SheetData());
		var sheets = spreadsheetDocument.WorkbookPart.Workbook.AppendChild<Sheets>(new Sheets());
		var sheet = new Sheet()
		{
			Id = spreadsheetDocument.WorkbookPart.GetIdOfPart(worksheetPart),
			SheetId = 1,
			Name = "myFirstSheet"
		};
		sheets.Append(sheet);
		workbookPart.Workbook.Save();
		spreadsheetDocument.Close();
	}
}

Observed

Office 365 encoding are all utf-8 without bom, but openxmlsdk some're utf-8 with bom and some not

Expected

Should we follow office365 encoding standard? (below image is office 365 xlsx)

office365_sample.xlsx

[twsouthwick]

We changed it to that as it was causing some renderers to have problems (see https://github.com/OfficeDev/Open-XML-SDK/issues/309).

I'm not certain if there's a specific encoding is required by the spec, but we could potentially enable it to be configurable rather than relying on a specific default.

[shps951023]

but we could potentially enable it to be configurable rather than relying on a specific default.

@twsouthwick Thanks! it will be helpful feature.

[twsouthwick]

Happy to accept PRs. Probably best to add it to the OpenSettings object

[tomjebo]

@shps951023 is there a good reason why the SDK should emit non-BOM UTF-8? From our Office apps team, it appears that we don't have any requirement either way, i.e. Office apps will read UTF-8 BOM parts just fine. Does your code depend on non-BOM UTF-8?

[shps951023]

@tomjebo So sorry about long time to see notification and to reply!! Some Chinese users need to custom encoding to read non-UTF8.

@twsouthwick Thanks, I'll try it

Happy new year! Wish everyone having a great new year.