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• [x] Question on library usage

Description

I added CustomFilePropertiesPart in an excel file using C# code, but after Save As this file in the machine new file doesn't show any CustomFilePropertiesPart in Open Xml Productivity Tool.

Information

• .NET Target: 4.5
• DocumentFormat.OpenXml Version: 2.8.1.0

Repro After Save as file CustomFilePropertiesPart property gets removed automatically. But some file doesn't remove properly. E6_P1_eStart.xlsx

Observed

After Save as file CustomFilePropertiesPart property gets removed automatically. But some file doesn't remove properly.

Expected

CustomFilePropertiesPart property should be in the new Save as a file.

I tried to reproduce your issue but I was unable to. I grabbed your sample file, ran the following:

            using (FileStream fs = new FileStream(@"E6_P1_eStart 2.xlsx", FileMode.Open, FileAccess.Read, FileShare.Read))
            {
                using (SpreadsheetDocument doc = SpreadsheetDocument.Open(fs, false))
                {
                    var studentProp = doc.CustomFilePropertiesPart.Properties.First() as CustomDocumentProperty;
                    var value = studentProp.InnerText;

                    Debug.WriteLine($"{studentProp.Name}: {value}");

                    doc.SaveAs(@"eStartSaveAs.xlsx");
                }
            }

            using (FileStream fs = new FileStream(@"eStartSaveAs.xlsx", FileMode.Open, FileAccess.Read, FileShare.Read))
            {
                using (SpreadsheetDocument doc = SpreadsheetDocument.Open(fs, false))
                {
                    var studentProp = doc.CustomFilePropertiesPart.Properties.First() as CustomDocumentProperty;
                    var value = studentProp.InnerText;

                    Debug.WriteLine($"{studentProp.Name}: {value}");
                }
            }

Which produced the output:

StudentID: 148924
StudentID: 148924

Are you able to provide more information on your issue?