[CONNECT C#] ElementChangedEvent and Item Types

Question

Versions: MicroStation Update 10 (10.10.00.23 and SDK 10.10.00.32). 
 I am trying to update an Item Type property on an element that has been moved. If I try to update the item type using a change event the code below will fail. If however, I put this code into a stand-alone command and get the collection of elements then the code runs fine. So, it seems that there is an issue updating the NewElement in the change event. 
 If I run it inside the change event, Change == ChangeTrackKind.Modify, the code that updates the ItemType crashes (full kill and closes MicroStation). This would be the ChangeStringPropertyOnItemType code. I thought maybe the Args.NewElement had not been written to the file yet, so I couldn't actually update it. Maybe I needed to update the Item Type when the modify was finished Change == 17 (by the way, this is missing from ChangeTrackKind). But the program still crashes when I try to make the update on Modify Finished. 
 static void ElementChangedInModel(object sender, ORDSignsApp.ElementChangedEventArgs Args)
{
 //...
 else if (Args.Change == AddIn.ChangeTrackKind.Modify) // move and change symbology
 {
 // test that this is a cell move otherwise return
 Element oldElm = Element.GetFromElementRef(Args.OldElementRef);
 if (!TestCellsAndEqualOrigins(oldElm, Args.NewElement)) return;

 // make sure we have cell that represents a post
 if (FdotSigns.HasPostItemType(Args.NewElement.ElementId))
 {
 // get current station label
 string s = FdotSigns.GetStringPropertyFromItemTypes(Args.NewElement, "SignPostIT", "Station");

 // is the station label populated
 if (s.Trim().Length > 0)
 {
 DPoint3d snapOrigin = new DPoint3d(.0, .0, .0);
 (Args.NewElement as CellHeaderElement).GetSnapOrigin(out snapOrigin);

 // set the active aligment - in this case the post alignment
 string aName = FdotSigns.GetStringPropertyFromItemTypes(Args.NewElement, "SignPostIT", "AlignmentName");
 if (FdotSigns.SetAlignmentFromName(aName))
 {
 // get the new station label
 string stationLabel = PlacementGuide.GetStation(FdotSigns.m_al, snapOrigin);

 // update station item type - fails when run from change event
 FdotSigns.ChangeStringPropertyOnItemType(Args.NewElement, stationLabel, "SignPostIT", "Station");
 }
 }
 }
 }
 //...
}

// update the item type property
public static void ChangeStringPropertyOnItemType(Bentley.DgnPlatformNET.Elements.Element elt, string newvalue, string itlib, string propname)
{
 try
 {
 CustomItemHost itemHost = new CustomItemHost(elt, false);
 IDgnECInstance appliedItem = itemHost.GetCustomItem("SignITL", itlib);

 if (appliedItem != null)
 {
 IECPropertyValue property = appliedItem.FindPropertyValue(propname, false, false, false);
 property.StringValue = newvalue;
 appliedItem.WriteChanges();
 }
 }
 catch (System.Exception ex)
 {
 ORDSignsApp.LogEx(ex);
 }
} 
 How do I know when the change event is really finished and NewElement has been written to the design file?

Jon Summers · Accepted Answer

Mark Stefanchuk said: I am trying to update an Item Type property on an element that has been moved. If I try to update the item type using a change event &hellip; 
 From MicroStationAPI help: 
 The Change Track API is NOT intended to enable applications to "influence" or modify the changes to the DGN file (that's the purpose of the SYSTEM_ELMDSCR_TO_FILE asynch call). Obviously, many applications can monitor te Change Track events simultaneously, and the order in which they are processed is indeterminate. However, since none of them can change the information being processed, the order of execution is moot. 
 So it's a bad idea to attempt to modify your Item Type properties in the ChangeTrackKind.Modify event handler. 
 The system callback ( SYSTEM_ELMDSCR_TO_FILE ) in the C++ MicroStationAPI is SetElmDscrToFileFunction . I don't know what the equivalent is in the DgnPlatformNet or MstnPlatformNet APIs.

[CONNECT C#] ElementChangedEvent and Item Types

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