Issue updating ContourImageSequence

[NickChng]

Describe the bug
Unable to replace ContourImageSequence. This exception is thrown:

System.InvalidOperationException: 'Unable to create DICOM element of type SQ with values of type Dicom.DicomSequence'

To Reproduce

The below attempts to replace the ContourImageSequence with itself (which I assume excludes any errors that may be attributable to user generation of the sequence). To be clear, it fails when I try to AddOrUpdate with a user-generated sequence as well.

// Get Sequence
var contourSequence = SSTemplate.Dataset.GetSequence(DicomTag.ReferencedFrameOfReferenceSequence).Items[0]
.GetSequence(DicomTag.RTReferencedStudySequence).Items[0]
.GetSequence(DicomTag.RTReferencedSeriesSequence).Items[0]
.GetSequence(DicomTag.ContourImageSequence);

// Set Sequence - this fails, even when replacing it with itself!
SSTemplate.Dataset.GetSequence(DicomTag.ReferencedFrameOfReferenceSequence).Items[0]
.GetSequence(DicomTag.RTReferencedStudySequence).Items[0]
.GetSequence(DicomTag.RTReferencedSeriesSequence).Items[0].
AddOrUpdate(DicomTag.ContourImageSequence, contourSequence);

Expected behavior
I expect this to work?

Environment
Fellow Oak DICOM version: 4.0.8
OS: Windows 10 x64
Platform: .NET Framework 4.8

[gofal]

The AddOrUpdate method is a facade for the various constructors. If you take a look at the constructor of DicomSequence then you see that it takes a list of DicomDatasets as parameter.
public DicomSequence(DicomTag tag, params DicomDataset[] items)

so you could either call
AddOrUpdate(DicomTag.ContourImageSequence, contourSequence.Items.ToArray());
or - because the variable contourSequence also contains the DicomTag - you can just call
AddOrUpdate(contourSequence);

[NickChng]

Thanks for the help!

In terms of my present issue sending only the contourSequence to the method has resolved the exception. In future I wonder if it might be more user-friendly to adjust the constructor to catch this during compile... DicomSequence presents an IEnumerable<DicomDataset> interface, which is presumably why it's accepted as a DicomDataset[]... it's not super obvious to beginners like me why it should work as a DicomItem but not IEnumerable<DicomDataset>.

At any rate, thanks again and I appreciate the quick response!