arcgis desktop - Selecting features by location based on selected feature using ArcObjects?

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?

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