/// <summary>
/// This method returns a FeatureDataTable containing all the rows from the shapefile that intersect the testGeometry.
/// The ShapeFile.ExecuteIntersectionQuery method only tests bounding boxes so we use the FilterDelegate property to add a true
/// intersection test using NetTopologySuite
/// </summary>
/// <param name="pathToShapefile">The path to the shapefile</param>
/// <param name="testGeometry">The geometry that we want to test against</param>
/// <returns></returns>
public FeatureDataTable GetIntersectingFeaturesUsingFilterDelegate(string pathToShapefile, SMGeometry testGeometry)
{
//create a new shapefile provider
using (ShapeFile shapefile = new ShapeFile(pathToShapefile))
{
//create an nts GeometryFactory
GeometryFactory geometryFactory = new GeometryFactory();
//convert the testGeometry into the equivalent NTS geometry
GeoAPI.Geometries.IGeometry testGeometryAsNtsGeom = GeometryConverter.ToNTSGeometry(testGeometry, geometryFactory);
SMGeometry check = GeometryConverter.ToSharpMapGeometry(testGeometryAsNtsGeom);
if (!check.Equals(testGeometry))
throw new ApplicationException("conversion error");
//set the shapefile providers' FilterDelegate property to a new anonymous method
//this delegate method will be called for each potential row
shapefile.FilterDelegate = delegate(FeatureDataRow featureDataRow)
{
//get the geometry from the featureDataRow
SMGeometry rowGeometry = featureDataRow.Geometry;
//convert it to the equivalent NTS geometry
GeoAPI.Geometries.IGeometry compareGeometryAsNtsGeometry =
GeometryConverter.ToNTSGeometry(rowGeometry, geometryFactory);
//do the test. Note that the testGeometryAsNtsGeometry is available here because it is
//declared in the same scope as the anonymous method.
bool intersects =
testGeometryAsNtsGeom.Intersects(compareGeometryAsNtsGeometry);
//return the result
return intersects;
};
//create a new FeatureDataSet
FeatureDataSet featureDataSet = new FeatureDataSet();
//open the shapefile
shapefile.Open();
//call ExecuteIntersectionQuery. The FilterDelegate will be used to limit the result set
shapefile.ExecuteIntersectionQuery(testGeometry, featureDataSet);
//close the shapefile
shapefile.Close();
//return the populated FeatureDataTable
return featureDataSet.Tables[0];
}
}
/// <summary>
/// This method takes a pre-populated FeatureDataTable and removes rows that do not truly intersect testGeometry
/// </summary>
/// <param name="featureDataTable">The FeatureDataTable instance to filter</param>
/// <param name="testGeometry">the geometry to compare against</param>
public void PostFilterExistingFeatureDataTable(FeatureDataTable featureDataTable, SMGeometry testGeometry)
{
//first we create a new GeometryFactory.
var geometryFactory = new GeometryFactory();
//then we convert the testGeometry into the equivalent NTS geometry
GeoAPI.Geometries.IGeometry testGeometryAsNtsGeom = GeometryConverter.ToNTSGeometry(testGeometry, geometryFactory);
//now we loop backwards through the FeatureDataTable
for (int i = featureDataTable.Rows.Count - 1; i > -1; i--)
{
//we get each row
FeatureDataRow featureDataRow = featureDataTable.Rows[i] as FeatureDataRow;
//and get the rows' geometry
SMGeometry compareGeometry = featureDataRow.Geometry;
//convert the rows' geometry into the equivalent NTS geometry
GeoAPI.Geometries.IGeometry compareGeometryAsNts = GeometryConverter.ToNTSGeometry(compareGeometry, geometryFactory);
//now test for intesection (note other operations such as Contains, Within, Disjoint etc can all be done the same way)
bool intersects = testGeometryAsNtsGeom.Intersects(compareGeometryAsNts);
//if it doesn't intersect remove the row.
if (!intersects)
featureDataTable.Rows.RemoveAt(i);
}
}
