NullReferenceException when copying sheet in some Excel files

[Paul1519]

Starting with version 2.5.1 I'm receiving the below Exception when cloning an existing sheet. This only seems to happen with some Excel files, not all of them (including those created by Microsoft Excel, some of them work). In this post I have attached an example of a file that fails with this exception.

Exception:

System.NullReferenceException: Object reference not set to an instance of an object.
at NPOI.POIXMLDocumentPart.AddRelation(PackageRelationship pr, POIXMLDocumentPart part)
at NPOI.POIXMLDocumentPart.AddRelation(String id, POIXMLDocumentPart part)
at NPOI.XSSF.UserModel.XSSFSheet.CopySheet(String name, Boolean copyStyle)
at NPOI.XSSF.UserModel.XSSFSheet.CopySheet(String Name)
at NPOITest.Program.Main(String[] args) in E:\Projects\VisualStudio\NPOITest\NPOITest\Program.cs:line 13

Example test code:

`

IWorkbook workbook = WorkbookFactory.Create("TestInput.xlsx");

workbook.GetSheetAt(0).CopySheet("Data");

using (FileStream fileWriter = new FileStream("TestOutput.xlsx", FileMode.Create, FileAccess.ReadWrite, FileShare.None))
{
    workbook.Write(fileWriter);
}

Console.WriteLine("Press enter to exit");
Console.ReadLine();

`

System Info:

Windows 10 Version 1909 (build 18363.778)
Visual Studio Enterprise 2019 version 16.5.4
Tested in both .NET Core 3.1 and .NET Framework 4.8
Microsoft Office Professional Plus 2019 (build 12624.20520) 32 bits

TestInput.xlsx

[tonyqus]

The issue is caused by printersettings xmlpart. I'll investigate it later

[KaarloHirvi]

Hi Tony, wonder if issue #346 is still there?

Had a similar test code as Paul1519 above. Crashes with NullReferenceException when trying to copy sheet.

Environment:
NPOI 2.5.4
Visual Studio 2017, .Net FrameWork 4.7, .NET Core SDK 2.1
Windows 10 Version 2004 x64 (KB5005565)
Excel for Microsoft 365 MSO (16.0.14326.20344) 32 bit

[tonyqus]

Can you upload your Excel file and let me know which sheet you are copying? @KaarloHirvi

[KaarloHirvi]

Thanks for replying.

Pls find attached the file. Was trying to copy sheet at [0]
pohja3.xlsx

[tonyqus]

@KaarloHirvi your issue duplicates with #287. copying sheets with charts will cause null exception.

[cp1319421]

Hi Tonyqus, i also have issue now, Crashes with NullReferenceException when trying to copy sheet

Environment:
NPOI 2.7.0
Visual Studio 2022, .Net 6.0
Windows 11 23H2
MSA_Templete.xlsx

[tonyqus]

@cp1319421 I double checked your Excel file. It contains charts. Even if it doesn't throw exception, charts will not be cloned to the new sheet.

[tonyqus]

I created a new issue #1338 for this. This issue will be closed