public void SetCamera( 
   Envelope extent
)

//Set the extent of a map frame to the envelope of a feature.

//Perform on the worker thread
await QueuedTask.Run(() =>
{
  //Reference MapFrame
  MapFrame mf_env = layout.FindElement("Map Frame") as MapFrame;

  //Get map and a layer of interest
  Map m = mf_env.Map;
  //Get the specific layer you want from the map and its extent
  FeatureLayer lyr = m.FindLayers("GreatLakes").First() as FeatureLayer;
  Envelope lyrEnv = lyr.QueryExtent();

  //Set the map frame extent to the feature layer's extent / envelope
  mf_env.SetCamera(lyrEnv);  //Note - you could have also used the lyr as an overload option
});

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

//Process on the worker thread
await QueuedTask.Run(() =>
{
  //Reference the mapframe and its associated map
  MapFrame mf = layout.FindElement("Map Frame") as MapFrame;
  Map m = mf.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;
        mf.SetCamera(env);

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