I'm using the Document Manager API alongside the regular Solidworks API to access the same model document. The reason for this dubious practice is that I need access to the InvisibleCustomProperty methods that the DM API provides and features of the model document. I'm not aware of a way of setting InvisibleCustomProperties through the normal Solidworks API.

My problem is that, when I set the property, save the document, and then re-open it. The invisible custom property doesn't exist anymore. This behavior isn't consistent - sometimes it does manage to save. If I rebuild the open Solidworks Model and then save it, the InvisibleCustomProperty is gone.

To combat this problem, every time I attempt to read from, write to, or create the InvisibleCustomProperty, I wrap the execution in this pair of functions:

Private Sub getDMDocWriteAccess()
    Dim open_error As SwDmDocumentOpenError
    Dim bRet As Boolean
   
    'make the model document read only before opening
    If pModel.IsOpenedReadOnly = False Then
        pModel.Save
        bRet = pModel.SetReadOnlyState(True): Debug.Assert bRet
        Debug.Print "Set the model document to read only"
    End If
   
    Debug.Assert Not (pModel.IsOpenedReadOnly = False)
    Set pDMDoc = pDMApp.GetDocument(pPathName, SwDmDocumentType.swDmDocumentPart, False, open_error)
    If Not open_error = swDmDocumentOpenErrorNone Then
        Set pDMDoc = pDMApp.GetDocument(pPathName, SwDmDocumentType.swDmDocumentPart, False, open_error): Debug.Assert open_error = swDmDocumentOpenErrorNone
    End If
   
End Sub 

Public Sub saveAndCloseDmDoc()
    Dim save_err        As SwDmDocumentSaveError
    Dim reload_err      As swComponentReloadError_e
    Dim swDMDocument    As SwDocumentMgr.swDMDocument
    Dim bRet            As Boolean
   
    Set swDMDocument = pDMDoc
   
    save_err = swDMDocument.Save: Debug.Assert save_err = swDmDocumentSaveErrorNone
    swDMDocument.CloseDoc
    bRet = pModel.SetReadOnlyState(False): Debug.Assert bRet
    reload_err = pModel.ReloadOrReplace(False, pModel.GetPathName, True): Debug.Assert ((reload_err = swDocumentNotChanged) Or (reload_err = swReloadOkay))
End Sub

For instance, setting the custom property is implemented in this way:

Public Sub setValue(value As String)
    getDMDocWriteAccess
    createCustomProperty
    pDMDoc.SetInvisibleCustomProperty pCustomPropertyName, value
    If Not (StrComp(pDMDoc.GetInvisibleCustomProperty(pCustomPropertyName, swDmCustomInfoText), value) = 0) Then
        pDMDoc.SetInvisibleCustomProperty pCustomPropertyName, value
    End If
    Debug.Assert (StrComp(pDMDoc.GetInvisibleCustomProperty(pCustomPropertyName, swDmCustomInfoText), value) = 0)
    
    Debug.Print "SET VALUE:" & pDMDoc.GetInvisibleCustomProperty(pCustomPropertyName, swDmCustomInfoText); ""
    
    saveAndCloseDmDoc
End Sub

These are all in a class with private variable names starting with "p" in those examples.

The macro runs without any of those debug.asserts throwing. However, the problem persists - the InvisibleCustomProperty does not persist.

The trouble I'm having with debugging this is I feel like I can't trust the return values for the DMDocument's save method and there isn't a way of observing the change when it is successful.

I would really prefer to use this functionality because it would prevent user-error and allow me to write future macros that use this value purely through the Document Manager API.