Creating Geometry Objects From Features

Spatial Filters

Spatial Filters

Updating Features

 

Creating Geometry Objects From Features

You may want to use an existing feature as part of a spatial query. To retrieve the feature’s geometry and convert it into an appropriate format for a query, perform the following steps:

• Create a query that will select the feature.
• Query the feature class containing the feature using AcMapLayer.SelectFeatures() or MgFeatureService.SelectFeatures().
• Obtain the feature from the query using the MgFeatureReader.ReadNext() method.
• Get the geometry data from the feature using the MgFeatureReader.GetGeometry() method. This data is in AGF binary format.
• Convert the AGF data to an MgGeometry object using the MgAgfReaderWriter.Read() method.

For example, the following sequence creates an MgGeometry object representing the boundaries of zone 1 in the layer named “zones”. It creates an MgGeometry object and the WKT representation of that object.

MgLayerCollection layers = currentMap.GetLayers();

MgLayerBase layer = layers.GetItem("zones");

string fsId = layer.GetFeatureSourceId();

string className = layer.GetFeatureClassName();

    
MgFeatureQueryOptions query =
    
  new MgFeatureQueryOptions();
    
query.SetFilter("ZONE_ID = 1");
    
MgResourceIdentifier resId =
    
  new MgResourceIdentifier(fsId);
    
 
    
MgFeatureReader featureReader =
    
  fs.SelectFeatures(resId,
    
   className, query);
    
if (featureReader.ReadNext())
    
{
    
  string geometryName = layer.GetFeatureGeometryName();
    
  MgByteReader geometryData = 
    
    featureReader.GetGeometry(geometryName);
    
  MgAgfReaderWriter agfReaderWriter = new MgAgfReaderWriter();
    
  MgGeometry geometry = agfReaderWriter.Read(geometryData);
    
 
    
  MgWktReaderWriter wktReaderWriter = new MgWktReaderWriter();
    
  string wkt = wktReaderWriter.Write(geometry);
    
}
  

The following assumes that another feature class has a geometry property SHPGEOM. It uses the WKT string in a query to find features in the other feature class that intersect the zone:

MgFeatureQueryOptions queryOpts = new MgFeatureQueryOptions();

queryOpts.SetFilter("SHPGEOM intersects GEOMFROMTEXT(" + 

  wkt + ")");