ArcObjects Selection – Selecting Features by Location in ArcObjects

arcgis-desktoparcobjectscselect-by-location

I am very new to ArcGIS and ArcObjects.

I am writing a code for a button that will detect a selected feature and then select other features based on the feature that I had selected please take a look at my code

public class LandmarkBtn : ESRI.ArcGIS.Desktop.AddIns.Button {

    public LandmarkBtn() {
    }

    protected override void OnClick() {
         var doc = ArcMap.Document;
        var focusMap = doc.FocusMap;
        IEnumLayer layer = focusMap.get_Layers(null,true);
        ILayer lyr = null;
        IFeatureClass Lmarks = null;

        while ((lyr = layer.Next()) != null) {

            var featureLayer = lyr as IFeatureLayer;
            if (featureLayer == null)
                continue;  



        var name = featureLayer.FeatureClass.AliasName;

            if ("landmarks".Equals(name.ToLowerInvariant())) {


                Lmarks = featureLayer.FeatureClass;
                break;
            }
        }

        if (Lmarks == null) {
            MessageBox.Show("Sorry, No LM Layer Found");
            return;
        }


        var selection = (IEnumFeature)focusMap.FeatureSelection;
        IFeature ftr = null;
        ftr = selection.Next();

ftr now holds the selected landmark(feature), I want to perform a query that will select features from another layer that are within 100 meters of the landmark feature, can you please direct me onto where I should look or provide me with a sample code that might help?

Best Answer

This will take multiple steps:

  1. Get a cursor from you selection set

        public static IFeatureCursor GetSelectedFeatures(IFeatureLayer featureLayer)
{
    if (featureLayer == null) return null;
    IFeatureSelection fSel = (IFeatureSelection)featureLayer;
    ISelectionSet selSet = (ISelectionSet)fSel.SelectionSet;
    ICursor cursor = null;
    selSet.Search(null, false, out cursor);
    IFeatureCursor fCursor = cursor as IFeatureCursor;
    return fCursor;
}

  2. Union and buffer the items in the cursor

    public static IPolygon UnionShapes(IFeatureCursor cursor, double bufferDist)
{
    if (cursor == null) return null;
    IFeature pFeat = cursor.NextFeature();
    if (pFeat != null)
    {
        if (pFeat.Shape is IPoint)
        {
            ITopologicalOperator ptopBuffer = (ITopologicalOperator)pFeat.Shape;
            IPolygon pTempPoly = (IPolygon)ptopBuffer.Buffer(bufferDist);
            ITopologicalOperator ptopUnion = (ITopologicalOperator)pTempPoly;
            pFeat = cursor.NextFeature();
            while (pFeat != null)
            {
                ptopBuffer = (ITopologicalOperator)pFeat.Shape;
                pTempPoly = (IPolygon)ptopBuffer.Buffer(bufferDist);
                ptopUnion = (ITopologicalOperator)ptopUnion.Union(pTempPoly);
                pFeat = cursor.NextFeature();
            }
            return (IPolygon)ptopUnion;
        }
        return null;
    }
    return null;
}

  3. Select the spatial filter on the new shape

       public static ISpatialFilter CreateSpatialFilter(IFeatureClass fc, IGeometry shape)
{
    if (fc == null) return null;
    ISpatialFilter sf = new SpatialFilterClass();
    sf.GeometryField = fc.ShapeFieldName;
    sf.Geometry = shape;
    sf.SpatialRel = esriSpatialRelEnum.esriSpatialRelIntersects;
    return sf;
}

  4. Search on the feature class with the filter.

        public static IFeatureCursor GetSelectedItemsByShape(IFeatureClass fc, ISpatialFilter filter)
{
    try
    {
        if (filter == null) return null;
        if (fc == null) return null;
        IFeatureCursor fcursor = fc.Search(filter, true);
        return fcursor;
    }
    catch
    {
        return null;
    }
}

  5. Then if you want to select the new features:

        public static ISelectionSet CursorToSelectionSet(IFeatureLayer layer, IFeatureCursor cursor)
{

    IFeatureSelection fSel = (IFeatureSelection)layer;
    if (cursor != null)
    {
        IFeature feat = cursor.NextFeature();
        while (feat != null)
        {
            fSel.Add(feat);
            feat = cursor.NextFeature();
        }
    }
    return fSel.SelectionSet;
}

Good Luck

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