[gdal-dev] Problem with adding Attributes to a point shapefile

[Henneke, Amanda M]

Hello-

I'm trying to create a point shapefile of all the first points in the polygons (from a poly shapefile) as shown below.  I also want to assign some attributes to the different point features.  I am having some issues doing this.  I get an error on the "feaPt.SetField("LAND_USE", sLandUse)" line that says "AccessViolationException was unhandled Attempted to read or write protected memory.  This is often an indication that other memory is corrupt".

If I take the attribute stuff out it runs fine and creates the shapefile.  I've done attribute adding before and this way has always worked for me, any ideas what I'm doing wrong???

      public void BuildShapefile(string sPolyShapeFile)
      {
         Ogr.RegisterAll();

         // Get driver for the shapefiles
         Driver drvShpFile = Ogr.GetDriverByName("ESRI Shapefile");

         // Create a Spatial Reference
         OSGeo.OSR.SpatialReference srGeo = new OSGeo.OSR.SpatialReference("");
         srGeo.SetGeogCS("Geographic Coordinate System", OSGeo.OSR.Osr.SRS_DN_WGS84, OSGeo.OSR.Osr.SRS_DN_WGS84, OSGeo.OSR.Osr.SRS_WGS84_SEMIMAJOR, OSGeo.OSR.Osr.SRS_WGS84_INVFLATTENING, "Greenwich", 0.0, "degree", 0.0174532925199433);

         // Create a datasource for the polygon file and for the new point file
         DataSource dsPolyShpFile = Ogr.Open(sPolyShapeFile, 0);
         DataSource dsPtShpFile = drvShpFile.CreateDataSource("D:\\Vector\\Output", new string[] { });

         // Create layers for the polygon file and the point file
         Layer lyrPoly = dsPolyShpFile.GetLayerByIndex(0);
         Layer lyrPt = dsPtShpFile.CreateLayer("Junk", srGeo, wkbGeometryType.wkbPoint, new string[] { });

         // Create Field Definition, Feature Definition and Features to enable us writing attributes to the new shapefile

         FeatureDefn feadefPt = lyrPt.GetLayerDefn();

         Feature feaPt = new Feature(feadefPt);
         Feature feaPoly;

         FieldDefn flddefLandUse = new FieldDefn("LAND_USE", FieldType.OFTString);

         flddefLandUse.SetWidth(100);

         //// Create an attribute field
         lyrPt.CreateField(flddefLandUse, 0);

         flddefLandUse.Dispose();

         // Create the Geometry for the new point file
         Geometry geoPoint = new Geometry(wkbGeometryType.wkbPoint);

         Geometry geoPoly = new Geometry(wkbGeometryType.wkbPolygon);
         Geometry geoPolyRing = new Geometry(wkbGeometryType.wkbLinearRing);

         int iFeaCount = lyrPoly.GetFeatureCount(1);

         // Loop through the poly file to get the points
         for (int iFea = 0; iFea < iFeaCount; iFea++)
         {
            feaPoly = lyrPoly.GetFeature(iFea);
            string sLandUse = feaPoly.GetFieldAsString("PGLANDUSE");
            geoPoly = feaPoly.GetGeometryRef();
            geoPolyRing = geoPoly.GetGeometryRef(0);

            // Add a point
            geoPoint.AddPoint(geoPolyRing.GetX(0), geoPolyRing.GetY(0), 0.0);
            feaPt.SetGeometry(geoPoint);

            // Set the attribute
            feaPt.SetField("LAND_USE", sLandUse);

            lyrPt.CreateFeature(feaPt);

            geoPoint.Empty();

            if (iFea == (iFeaCount - 1))
               feaPoly.Dispose();
         }
         geoPolyRing.Dispose();
         geoPoly.Dispose();
         geoPoint.Dispose();
         feaPt.Dispose();
         feadefPt.Dispose();
         lyrPoly.Dispose();
         lyrPt.Dispose();
         dsPolyShpFile.Dispose();
         dsPtShpFile.Dispose();
         srGeo.Dispose();
         drvShpFile.Dispose();
      }

Thanks,
Amanda M. Henneke




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