IBufferConstruction.ConstructBuffersByDistances2 - Memory Read/Write Error

Discussion created by JKnieriem on Aug 14, 2012
Latest reply on Aug 14, 2012 by JKnieriem
I have a polyline layer that needs to be buffered a specific direction (left or right of the line) and a specific distance.  The polyline layer has fields in the attribute table that define each of these criteria for each feature.  Buffers generally range from 12-35 feet. After the variable buffers are created, I need all overlapping sections to be dissolved.  I figured the IBufferConstruction.ConstructBuffersByDistances2() method was the way to go, but I haven't found any working samples out there that use this method.

The help page for the method here: ConstructBuffersByDistances2() says

[INDENT]If you wish to apply a different buffer distance to each input geometry, you can use the ConstructBuffersByDistances2 method, which requires that inputs and outputs be staged in memory first[/INDENT]

I'm fairly new to C# and ArcObjects in general, so I'm guessing this is where my problem lies and I don't know how to fix it!  The feature cursor loop fills out the GeometryBag and DoubleArray properly.  When it gets to the final line of code though, it generates the error message: "Attempted to read or write protected memory". 

The other option, according to the help, would be to implement the IGeometricBufferSourceSink interface.  I couldn't find any code examples of that either.  Any help would be appreciated!

                IGeometryCollection lineGeoBagColl = new GeometryBagClass();
                IDoubleArray pDoubleArray = new DoubleArrayClass();
                IFeatureCursor _lineFCursor = _inputLineLayer.Search(null, false);                
                IGeometryCollection pOutputGeoColl = new GeometryBagClass();
                IFeature _Feat = _lineFCursor.NextFeature();

                using (ESRI.ArcGIS.ADF.ComReleaser comReleaser = new ComReleaser())

                        Boolean isManaged = false;
                        if (!isManaged)
                            isManaged = true;

                        IRow pRow = _Feat;
                        IPolyline pPolyline = _Feat.ShapeCopy as IPolyline;

                        // Gets the distance from the distance field and adds it to the array.
                        double offsetDistance = (double)pRow.get_Value(_OffsetFieldIndex);

                        // Gets the value in the direction field.  
                        // If the value is L or Left, it will reverse orientation of the line.
                        // The final buffers will all be generated to the right.
                        string offsetDirection = pRow.get_Value(_OffsetDirectionFieldIndex).ToString();
                        offsetDirection = offsetDirection.Trim().ToUpper();
                        if (offsetDirection == "L" || offsetDirection == "LEFT")
                        lineGeoBagColl.AddGeometryCollection(pPolyline as IGeometryCollection);

                        _Feat = _lineFCursor.NextFeature();

                    } while (_Feat != null);


                IBufferConstruction bc = new BufferConstructionClass();
                IBufferConstructionProperties bcProp = bc as IBufferConstructionProperties;
                bcProp.SideOption = esriBufferConstructionSideEnum.esriBufferRight;
                bcProp.UnionOverlappingBuffers = true;
                bcProp.ExplodeBuffers = true;
                bcProp.EndOption = esriBufferConstructionEndEnum.esriBufferRound;

                IEnumGeometry pEnumGeo = lineGeoBagColl as IEnumGeometry;

                bc.ConstructBuffersByDistances2(pEnumGeo, pDoubleArray, pOutputGeoColl);