spatial query based on mouse click event

Question

Please look the code , I  wish to access the feature at the mouse coordinate on mouse click event. however my code below return all the records rather than a single point. any guess what is wrong.

IMxApplication pMxApp = null;
            pMxApp = (IMxApplication)ArcMap.Application;
            IMxDocument pMxDoc = null;

pMxDoc = ArcMap.Document;
            if (pMxDoc.SelectedLayer == null)
            {
                MessageBox.Show("There is no layer selected.  First select a time-aware layer.");
                return;
            }
            IMap pMap = pMxDoc.FocusMap;
            IFeatureLayer feature_layer = (IFeatureLayer)pMap.get_Layer(0);// put the index of ur lauer
            IPoint point = new PointClass();

x = pMxDoc.CurrentLocation.X; // this is point returns when user click on mouse.
            y = pMxDoc.CurrentLocation.Y;
            MessageBox.Show(x+ ":" + y);
            point.PutCoords(x, y);
            // point.PutCoords(280, 240);
            point.SpatialReference = pMap.SpatialReference;
            ISpatialFilter spatial_filter = new SpatialFilterClass();
            spatial_filter.SpatialRel = esriSpatialRelEnum.esriSpatialRelIntersects;
            spatial_filter.Geometry = point;
            spatial_filter.GeometryField = feature_layer.FeatureClass.ShapeFieldName;
            MessageBox.Show(spatial_filter.GeometryField.ToString());
            IFeatureCursor feature_cursor = feature_layer.FeatureClass.Search(spatial_filter, false);
            IFeature feature = feature_cursor.NextFeature();
          
            while (feature != null)   // here it returns the whole records rather than single point.
            {
                // do what u wan0t with the feature
                MessageBox.Show(feature.get_Value(3).ToString());
                feature = feature_cursor.NextFeature();
            }
        }
 
    
    }

CarstenSchumann · Answer

Depending on your map-coordinate system you should also transform your coordinates returned from your mouse-position into real world coords before doing any buffer (as mentioned by Barbara Schneider‌) or calculating any near features (see @Bill Brodie)

BillBrodie · Answer

Here is a C# function I have used to find the nearest feature from a layer. It buffers an input point to make the spatial query geometry, then determines which intersecting feature is closest - return just that one feature. Hope it helps. ///

Find the nearest feature in the layer from a point within a maximum distance ///

/// Layer to search /// Point to search near /// Maximum distance /// Nearest feat or null if none within the maximum distance public static IFeature GetNearestFeature(IFeatureLayer searchLayer, IPoint nearPoint, double maxDistance) { //todo: get the feature class and call the primary overload ... ITopologicalOperator topo = (ITopologicalOperator)nearPoint; IProximityOperator prox = (IProximityOperator)nearPoint; IFeature nearFeat = null; double nearDist = 0; string saveDefinitionQuery = string.Empty; if (string.IsNullOrEmpty(((IFeatureLayerDefinition)searchLayer).DefinitionExpression)) { saveDefinitionQuery = ((IFeatureLayerDefinition)searchLayer).DefinitionExpression; ((IFeatureLayerDefinition)searchLayer).DefinitionExpression = string.Empty; } ISpatialFilter filter = new SpatialFilterClass(); try { filter.Geometry = topo.Buffer(maxDistance); filter.GeometryField = searchLayer.FeatureClass.ShapeFieldName; filter.SpatialRel = esriSpatialRelEnum.esriSpatialRelIntersects; } catch (Exception ex) { //todo: handle this } finally { //restore the definition query ((IFeatureLayerDefinition)searchLayer).DefinitionExpression = saveDefinitionQuery; } IFeatureCursor cursor = searchLayer.Search(filter, false); try { IFeature testFeat = null; while ((testFeat = cursor.NextFeature()) != null) { double testDist = prox.ReturnDistance(testFeat.Shape); if (testDist < nearDist || nearFeat == null) { nearFeat = testFeat; nearDist = testDist; } } } catch (Exception ex) { //todo:handle } finally { Marshal.ReleaseComObject(cursor); } return nearFeat; } Good Luck

BarbaraSchneider1 · Answer

Hello,

what type of layer do you query (IFeatureLayer feature_layer = (IFeatureLayer)pMap.get_Layer(0)) ? Is it a point layer? If so, you will never get the exact point using this query. You will have to apply a scale dependent buffer to your mouse point, e.g.:IEnvelope env = new EnvelopeClass();
env.SpatialReference = pMap.SpatialReference;
env.PutCoords(x - ..., y - ..., x + ..., y + ...);
...
spatial_filter.Geometry = env;

Does this help?

Barbara