public IReadOnlyList<Layer> FindLayers( 
   string name,
   bool recursive
)

// Finds and retrieves specific editing templates by name from layers in the active map.
await QueuedTask.Run(() =>
{
  var mainTemplate = activeMap.FindLayers("main").FirstOrDefault()?.GetTemplate("Distribution");
  var mhTemplate = activeMap.FindLayers("Manhole").FirstOrDefault()?.GetTemplate("Active");
});

{
  //Create a table frame.
  //Note: Must be on QueuedTask.Run

  //Build 2D envelope geometry
  Coordinate2D rec_ll = new Coordinate2D(1.0, 3.5);
  Coordinate2D rec_ur = new Coordinate2D(7.5, 4.5);
  Envelope rec_env = EnvelopeBuilderEx.CreateEnvelope(rec_ll, rec_ur);

  //Reference map frame and layer
  MapFrame mf = layout.FindElement("Map Frame") as MapFrame;
  FeatureLayer lyr = mf.Map.FindLayers("GreatLakes").First() as FeatureLayer;

  //Build fields list
  var fields = new[] { "NAME", "Shape_Area", "Shape_Length" };

  //Construct the table frame

  var tableFrameInfo = new TableFrameInfo()
  {
    FieldNames = fields,
    MapFrameName = mf.Name,
    MapMemberUri = lyr.URI
  };
  var tabFrame = ElementFactory.Instance.CreateMapSurroundElement(
    layout, rec_env, tableFrameInfo) as TableFrame;
}

{
  //Zoom map frame to the extent of a single layer.

  //Note: Must be on QueuedTask.Run
  //Reference map and layer
  Map m = mapFrame.Map;
  FeatureLayer lyr = m.FindLayers("GreatLakes").First() as FeatureLayer;

  //Set the map frame extent to all features in the layer
  mapFrame.SetCamera(lyr, false);
}

{
  //Change the extent of a map frame to the selected features multiple layers.
  //Note: Must be on QueuedTask.Run
  //Reference MapFrame

  //Reference map, layers and create layer list
  Map m = mapFrame.Map;
  FeatureLayer fl_1 = m.FindLayers("GreatLakes").First() as FeatureLayer;
  FeatureLayer fl_2 = m.FindLayers("States_WithRegions").First() as FeatureLayer;
  var layers = new[] { fl_1, fl_2 };
  //IEnumerable<Layer> layers = m.Layers;  //This creates a list of ALL layers in map.

  //Set the map frame extent to the selected features in the list of layers
  mapFrame.SetCamera(layers, true);
}

{
  //Change map frame extent to single feature with 10 percent buffer

  //Note: Must be on QueuedTask.Run

  //Reference the mapframe and its associated map
  Map m = mapFrame.Map;

  //Reference a feature layer and build a query (to return a single feature)
  FeatureLayer fl = m.FindLayers("GreatLakes").First() as FeatureLayer;
  QueryFilter qf = new QueryFilter();
  string whereClause = "NAME = 'Lake Erie'";
  qf.WhereClause = whereClause;

  //Zoom to the feature
  using (ArcGIS.Core.Data.RowCursor rowCursor = fl.Search(qf))
  {
    while (rowCursor.MoveNext())
    {
      //Get the shape from the row and set extent
      using (var feature = rowCursor.Current as ArcGIS.Core.Data.Feature)
      {
        Polygon polygon = feature.GetShape() as Polygon;
        Envelope env = polygon.Extent as Envelope;
        mapFrame.SetCamera(env);

        //Zoom out 15 percent
        Camera cam = mapFrame.Camera;
        cam.Scale = cam.Scale * 1.15;
        mapFrame.SetCamera(cam);
      }
    }
  }
}

{
    //Finds layers by name and returns a read only list of Layers
    IReadOnlyList<Layer> layers = map.FindLayers("cities", true);

    //Finds a layer using a URI.
    //The Layer URI you pass in helps you search for a specific layer in a map
    var lyrFindLayer = MapView.Active.Map.FindLayer("CIMPATH=map/u_s__states__generalized_.xml");

    //This returns a collection of layers of the "name" specified. You can use any Linq expression to query the collection.  
    var lyrExists = MapView.Active.Map.GetLayersAsFlattenedList()
                       .OfType<FeatureLayer>().Any(f => f.Name == "U.S. States (Generalized)");
}