Qfyilyi

AutoCAD 2015 - I am currently learning the .NET API for creating geometric constraints (note: I am no stranger to AutoCAD API in general). I am working with a code sample I got from one of the AutoDesk courses to learn from, and I can't seem to figure out why I am getting a "FATAL ERROR" and crash when trying to retrieve an entity's vertices with GetEdgeVertexSubentities(..). There is no Exception thrown, Autocad just pops up the message and crashes. Try/Catch doesn't do anything, so can't inspect the exception message or the call stack. If anyone has seen this before or has some ideas as what I can look at or try, it would be much appreciated.

This happens with and without the debugger attached. In other words, same error occurs with a release build, launched from a shortcut.

I've tried using a different drawing, different computer, and even different OS (ie Win7, Win10), all having the same end result. Error message below and crash.

Visual Studio Output Window message:

Exception thrown: 'System.AccessViolationException' in AcdbMgd.dll

And the error message pop-up:

Here's the full test command. The offending line of code is clearly marked, about half way down the code snippet.

using System;

using System.Collections.Generic;

using Autodesk.AutoCAD.Runtime;

using Autodesk.AutoCAD.ApplicationServices;

using Autodesk.AutoCAD.DatabaseServices;

using Autodesk.AutoCAD.Geometry;

using Autodesk.AutoCAD.EditorInput;



[CommandMethod("TESTFIXED")]

public static void testFixedCommand()

{

  Database db = Application.DocumentManager.MdiActiveDocument.Database;

  Autodesk.AutoCAD.DatabaseServices.TransactionManager tm = db.TransactionManager;

  using (Transaction transaction = tm.StartTransaction())

  {

    // Create DB resident line

    BlockTable blockTable = (BlockTable)transaction.GetObject(db.BlockTableId, OpenMode.ForRead, false);

    BlockTableRecord modelSpace = (BlockTableRecord)transaction.GetObject(blockTable[BlockTableRecord.ModelSpace], OpenMode.ForWrite, false);

    Entity entity = new Line(new Point3d(12, 5, 0), new Point3d(15, 12, 0));

    modelSpace.AppendEntity(entity);

    transaction.AddNewlyCreatedDBObject(entity, true);



    AssocPersSubentityIdPE subentityIdPE;

    RXClass protocolClass = AssocPersSubentityIdPE.GetClass(typeof(AssocPersSubentityIdPE));

    IntPtr pSubentityIdPE = entity.QueryX(protocolClass);

    if (pSubentityIdPE == IntPtr.Zero)

    {

        return;

    }

    subentityIdPE = AssocPersSubentityIdPE.Create(pSubentityIdPE, false) as AssocPersSubentityIdPE;

    if (subentityIdPE == null)

    {

      return;

    }

    // Now we have the PE, we query the subentities

    // First we retrieve a list of all edges (a line has one edge)

    SubentityId edgeSubentityIds = null;

    edgeSubentityIds = subentityIdPE.GetAllSubentities(entity, SubentityType.Edge);

    SubentityId test = edgeSubentityIds[0];

    SubentityId startSID = SubentityId.Null;

    // Now we retrieve the vertices associated with the first edge in our array.

    // In this case we have one edge, and the edge has three vertices - start, end and middle.

    SubentityId endSID = SubentityId.Null;

    SubentityId other = null;



//****** This next line is the offender ********

    subentityIdPE.GetEdgeVertexSubentities(entity, test, ref startSID, ref endSID, ref other);

//************************************************



    // The PE returns a SubEntId. We want a FullSubentityPath

    FullSubentityPath subentPathEdge = new FullSubentityPath(new ObjectId[1] { entity.ObjectId }, edgeSubentityIds[0]); // The line edge

    FullSubentityPath subentPath1 = new FullSubentityPath(new ObjectId[1] { entity.ObjectId }, startSID); // The edge's startpoint.



    // We call a helper function to retrieve or create a constraints group

    ObjectId constraintGroupID = getConstraintGroup(true);

    using (Assoc2dConstraintGroup constraintGroup = (Assoc2dConstraintGroup)transaction.GetObject(constraintGroupID, OpenMode.ForWrite, false))

    {

      // Pass in geometry to constrain (the line edge)

      ConstrainedGeometry constraintedGeometry = constraintGroup.AddConstrainedGeometry(subentPathEdge);

      // Now create the constraint, a Fixed constraint applied to the line's startpoint.

      FullSubentityPath paths = new FullSubentityPath[1] { subentPath1 };

      GeometricalConstraint newConstraint = constraintGroup.AddGeometricalConstraint(GeometricalConstraint.ConstraintType.Fix, paths);

    }



    // Evaluate the network to update the parameters of the constrained geometry

    String temp = "";

    ObjectId networkId = AssocNetwork.GetInstanceFromDatabase(db, true, temp);

    using (AssocNetwork network = (AssocNetwork)transaction.GetObject(networkId, OpenMode.ForWrite, false))

    {

      AssocEvaluationCallback callBack = null;

      network.Evaluate(callBack);

    }

    transaction.Commit();

  }

}

To run that command, you will also need this helper method. There are no known issues with the code below, just copy and paste.

// Helper function to retrieve (or create) constraint group

internal static ObjectId getConstraintGroup(bool createIfDoesNotExist)

{

    // Calculate the current plane on which new entities are added by the editor

    // (A combination of UCS and ELEVATION sysvar).

    Editor editor = Application.DocumentManager.MdiActiveDocument.Editor;

    Matrix3d ucsMatrix = editor.CurrentUserCoordinateSystem;

    Point3d origin = ucsMatrix.CoordinateSystem3d.Origin;

    Vector3d xAxis = ucsMatrix.CoordinateSystem3d.Xaxis;

    Vector3d yAxis = ucsMatrix.CoordinateSystem3d.Yaxis;

    Vector3d zAxis = ucsMatrix.CoordinateSystem3d.Zaxis;

    origin = origin + Convert.ToDouble(Application.GetSystemVariable("ELEVATION")) * zAxis;

    Plane currentPlane = new Plane(origin, xAxis, yAxis);



    // get the constraint group from block table record

    ObjectId ret = ObjectId.Null;

    Database database = HostApplicationServices.WorkingDatabase;

    ObjectId networkId = AssocNetwork.GetInstanceFromObject(SymbolUtilityServices.GetBlockModelSpaceId(database), createIfDoesNotExist, true, "");

    if (!networkId.IsNull)

    {

        // Try to find the constraint group in the associative network

        using (Transaction transaction = database.TransactionManager.StartTransaction())

        {

            using (AssocNetwork network = transaction.GetObject(networkId, OpenMode.ForRead, false) as AssocNetwork)

            {

                if (network != null)

                {

                    // Iterate all actions in network to find Assoc2dConstraintGroups

                    ObjectIdCollection actionsInNetwork = network.GetActions;

                    for (int nCount = 0; nCount <= actionsInNetwork.Count - 1; nCount++)

                    {

                        ObjectId idAction = actionsInNetwork[nCount];

                        if (idAction == ObjectId.Null)

                        {

                            continue;

                        }



                        // Is this action a type of Assoc2dConstraintGroup?

                        if (idAction.ObjectClass.IsDerivedFrom(RXObject.GetClass(typeof(Assoc2dConstraintGroup))))

                        {

                            using (AssocAction action = (AssocAction)transaction.GetObject(idAction, OpenMode.ForRead, false))

                            { 

                                if (action == null)

                                {

                                    continue;

                                }



                                Assoc2dConstraintGroup constGrp = action as Assoc2dConstraintGroup;

                                // Is this the Assoc2dConstraintGroup for our plane of interest?

                                if (constGrp.WorkPlane.IsCoplanarTo(currentPlane))

                                {

                                    // If it is then we've found an existing constraint group we can use.

                                    ret = idAction;

                                    break;

                                }

                            }

                        }

                    }

                }

            }



            // If we get to here, a suitable contraint group doesn't exist, create a new one if that's what calling fn wanted.

            if (ret.IsNull && createIfDoesNotExist)

            {

                using (AssocNetwork network = (AssocNetwork)transaction.GetObject(networkId, OpenMode.ForWrite, false))

                {

                    // Create  construction plane

                    Plane constraintPlane = new Plane(currentPlane);

                    // If model extent is far far away from origin then we need to shift

                    // construction plane origin within the model extent.

                    // (Use Pextmin, PExtmax in paper space)

                    Point3d extmin = database.Extmin;

                    Point3d extmax = database.Extmax;

                    if (extmin.GetAsVector().Length > 100000000.0)

                    {

                        Point3d originL = extmin + (extmax - extmin) / 2.0;

                        PointOnSurface result = currentPlane.GetClosestPointTo(originL);

                        constraintPlane.Set(result.GetPoint(), currentPlane.Normal);

                    }

                    // Create the new constraint group and add it to the associative network.

                    using (Assoc2dConstraintGroup constGrp = new Assoc2dConstraintGroup(constraintPlane))

                    {

                        ret = database.AddDBObject(constGrp);

                    }

                    network.AddAction(ret, true);

                }

            }

            transaction.Commit();

        }

    }

    return ret;

}

(I wanted to add this as comment but I am not eligible for commenting yet)
I think it has to do with your Visual Studio settings. My suggestion would be to double check Properties -> Debugging. I had similar problem with one of my add-ins and it started working as expected after I added Working Directory and fixed Command Line Argument in Debugging settings.