public double Scale {get; set;}

{
  //Change a map frame's camera settings.

  //Reference MapFrame
  MapFrame mf = layout.FindElement("Map Frame") as MapFrame;

  //Reference the camera associated with the map frame and change the scale
  Camera cam = mf.Camera;
  cam.Scale = 100000;

  //Set the map frame extent based on the new camera info
  mf.SetCamera(cam);
}

{
  //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);
      }
    }
  }
}