Zignoruj ostrzeżenie OpenXML
IgnoredErrors ignoredErrors = new IgnoredErrors();
IgnoredError ignoredError = new IgnoredError()
{
SequenceOfReferences = new ListValue<StringValue> { InnerText = "A:Z" },
NumberStoredAsText = true
};
ignoredErrors.Append(ignoredError);
worksheetPart.Worksheet.Append(ignoredErrors);
sheets.Append(sheet);
Sore Stork