[CONNECT U16 C#] How to copy element from one model into a new DGN? (Add-in crashes on dgnFile.ProcessChanges)

Question

Hi, as a follow-up to this thread , I'm trying to copy an element from an currently opened DGN file to a new temporary DGN file in order to export the single element (normally a cell) as an FBX file. 
 According to suggestions that I've read in this forum, I'm trying to attach the respective DGN model to the temporary file and then use ElementCopyContext to copy the element to the new model. 
 
 Here's my method that accepts a file path for the new DGN file, the source model and the element to copy: 
 private void CopyElementToNewFile(string newDgnFilePath, DgnModel sourceModel, Element sourceElement)
 {
 DgnModelStatus error;
 DgnFileStatus status = 0;

 // create new DgnDocument (still in-memory)
 using (DgnDocument targetDgnDocument = DgnDocument.CreateForNewFile(out status, newDgnFilePath, null,0, null ,DgnDocument.OverwriteMode.Always, DgnDocument.CreateOptions.Default))
 {
 if (status != DgnFileStatus.Success)
 {
 ShowMessage(msg: $"Error creating new file: {status}");
 return;
 }

 using (DgnFileOwner dgnFileOwner = DgnFile.Create(document: targetDgnDocument, openMode: DgnFileOpenMode.ReadWrite))
 {
 DgnFile dgnFile = dgnFileOwner.DgnFile;

 // create a new model based on the source model
 DgnModel targetDgnModel = dgnFile.CreateNewModel(error: out error, name: "Default",type: DgnModelType.Normal,is3D: true, seedModel: sourceModel);

 if (error != DgnModelStatus.Success)
 {
 ShowMessage(msg: $"Error creating new model: {error}");
 return;
 }
 
 var sourceFileName = sourceModel.GetDgnFile().GetFileName();
 DgnDocumentMoniker sourceDgnDocumentMoniker = DgnDocumentMoniker.CreateFromFileName(fileName: sourceFileName, searchPath: null);

 // attach the source model to the new model 
 DgnAttachment attachment = targetDgnModel.CreateDgnAttachment(moniker: sourceDgnDocumentMoniker, modelName: sourceModel.ModelName);
 var attachedModel = attachment.GetDgnModel();

 // find the element to copy in the attached model (maybe just use sourceElement directly?)
 var elementInAttachedModel = attachedModel.FindElementById(sourceElement.ElementId); 
 if (elementInAttachedModel == null)
 {
 ShowMessage(msg: $"Error. Could not find element by ID.");
 }

 // copy the element to the new model
 using (ElementCopyContext cc = new ElementCopyContext(dgnModelRef: targetDgnModel))
 {
 cc.DoCopy(elementInAttachedModel);
 }

 // process the changes, method should write the file to disc
 var result = dgnFile.ProcessChanges(reason: DgnSaveReason.UserInitiated); // add-in crashes
 // AccessViolation in Bentley::DgnPlatform::DgnExclusiveLock::DgnExclusiveLock+0xa 
 }
 }
 } 
 
 S adly, the add-in crashes on dgnFile.ProcessChanges() , inst antly followed by an error report dialog in Microstation. Try/catch yielded nothing. Microstation's exception log shows an Access violation at Bentley::DgnPlatform::DgnExclusiveLock::DgnExclusiveLock Any hints about what I'm doing wrong are appreciated. If another approach or another set of API methods is more suitable, please advise. 
 Thanks, Regards, 
 Lars

Jan Šlegr · Accepted Answer

Hi Lars, 
 Lars Kriev said: Any hints about what I'm doing wrong are appreciated. 
 I returned to this discussion (found some time to think about it ;-) and I am still thinking your code is over-complicated. 
 Lars Kriev said: That looks easy, but it gets ugly when you try it with managed code. 
 I do not think it is ugly, but it is true that API is low level, so simple task "create and use file" must be implemented as several steps. 
 I think there are more ways how to create new file from seed, one solution is this (simplified): 
 // seedFile: Full path to seed file (c:\files\myseed.dgn)
// newFilePath: Full path to new file (c:\files
ewfile.dgn)


StatusInt status = StatusInt.Error;

using (DgnDocument document = DgnDocument.CreateForLocalFile(seedFile))
using (DgnFileOwner owner = DgnFile.Create(document, DgnFileOpenMode.ReadOnly))
{
 DgnFile dgnFile = owner.DgnFile;
 StatusInt openForWriteStatus;
 DgnFileStatus fileStatus = dgnFile.LoadDgnFile(out openForWriteStatus);

 if (fileStatus == DgnFileStatus.Success)
 {
 using (DgnDocument newDocument = DgnDocument.CreateForLocalFile(newFilePath))
 {
 status = dgnFile.DoSaveAs(newDocument, DgnFileFormatType.V8, false, false);
 }
 }

 return status;
} 
 Lars Kriev said: If another approach or another set of API methods is more suitable, please advise. 
 As I wrote in my previous comment, the copying is simple process, because when set right, API (copy context) does everything for you. 
 Code to copy all cells from active model to (existing) external file, opened at background (no attaching or anything else is required): 
 // targetLocation: Full path to existing target file (c:\files
ewfile.dgn)

using (DgnDocument document = DgnDocument.CreateForLocalFile(targetLocation))
using (DgnFileOwner owner = DgnFile.Create(document, DgnFileOpenMode.ReadWrite))
{
 DgnFile targetDgn = owner.DgnFile;

 StatusInt openForWriteStatus;
 DgnFileStatus loadDgnStatus = targetDgn.LoadDgnFile(out openForWriteStatus);

 ModelIndexCollection indexes = targetDgn.GetModelIndexCollection();

 StatusInt errorDetails;
 DgnModel targetModel = targetDgn.LoadRootModelById(out errorDetails, 0);

 DgnModel activeModel = Session.Instance.GetActiveDgnModel();
 ModelElementsCollection elements = activeModel.GetGraphicElements();

 using (ElementCopyContext context = new ElementCopyContext(targetModel))
 {
 foreach (var element in elements)
 {
 if (element is CellHeaderElement cell)
 {
 context.DoCopy(cell);
 }
 }
 }

 targetDgn.ProcessChanges(DgnSaveReason.FileClose);
} 
 Of course, real code should be implemented in more robust way to ensure every step is checked for its result / status. 
 With regards, 
 Jan

[CONNECT U16 C#] How to copy element from one model into a new DGN? (Add-in crashes on dgnFile.ProcessChanges)

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