public T FindClosestElement<T>( 
   MapPoint queryPoint,
   double searchRadius
)
where T: TopologyElement

{
  static void FindClosestElement()
  {
    using (Geodatabase geodatabase = new Geodatabase(new FileGeodatabaseConnectionPath(new Uri(@"C:\TestData\GrandTeton.gdb"))))
    using (ArcGIS.Core.Data.Topology.Topology topology = geodatabase.OpenDataset<ArcGIS.Core.Data.Topology.Topology>("Backcountry_Topology"))
    {
      // Build a topology graph using the extent of the topology dataset.
      topology.BuildGraph(topology.GetExtent(), (topologyGraph) =>
      {
        MapPoint queryPointViaCampsites12 = null;

        using (Feature campsites12 = GetFeature(geodatabase, "Campsites", 12))
        {
          queryPointViaCampsites12 = campsites12.GetShape() as MapPoint;
        }

        double searchRadius = 1.0;

        TopologyElement topologyElementViaCampsites12 = topologyGraph.FindClosestElement<TopologyElement>(queryPointViaCampsites12, searchRadius);
        IReadOnlyList<FeatureInfo> parentFeatures = topologyElementViaCampsites12.GetParentFeatures();

        Console.WriteLine("The parent features that spawn 'topologyElementViaCampsites12' are:");
        foreach (FeatureInfo parentFeature in parentFeatures)
        {
          Console.WriteLine($"\t{parentFeature.FeatureClassName}; OID: {parentFeature.ObjectID}");
        }

        TopologyNode topologyNodeViaCampsites12 = topologyGraph.FindClosestElement<TopologyNode>(queryPointViaCampsites12, searchRadius);

        if (topologyNodeViaCampsites12 != null)
        {
          // There exists a TopologyNode nearest to the query point within searchRadius units.
        }

        TopologyEdge topologyEdgeViaCampsites12 = topologyGraph.FindClosestElement<TopologyEdge>(queryPointViaCampsites12, searchRadius);

        if (topologyEdgeViaCampsites12 != null)
        {
          // There exists a TopologyEdge nearest to the query point within searchRadius units.
        }
      });
    }
  }
}