public Geometry GetShape()

{
  // methods need to run on the MCT
  ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(() =>
  {
    try
    {
      // open a gdb
      using (ArcGIS.Core.Data.Geodatabase gdb =
                new ArcGIS.Core.Data.Geodatabase(
                    new FileGeodatabaseConnectionPath(new Uri(@"c:\Temp\MyDatabase.gdb"))))
      {
        //Open a featureClass 
        using (ArcGIS.Core.Data.FeatureClass featureClass =
                       gdb.OpenDataset<ArcGIS.Core.Data.FeatureClass>("Polygon"))
        {

          ArcGIS.Core.Data.QueryFilter filter =
                     new ArcGIS.Core.Data.QueryFilter()
                     {
                       WhereClause = "OBJECTID = 6"
                     };

          // get the row
          using (ArcGIS.Core.Data.RowCursor rowCursor =
                                 featureClass.Search(filter, false))
          {
            while (rowCursor.MoveNext())
            {
              using (var row = rowCursor.Current)
              {
                long oid = row.GetObjectID();

                // get the shape from the row
                ArcGIS.Core.Data.Feature feature = row as ArcGIS.Core.Data.Feature;
                Polygon polygon = feature.GetShape() as Polygon;

                // do something here
              }
            }
          }
        }
      }
    }
    catch (Exception ex)
    {
      // error - handle appropriately
    }
  });
}

{
  //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);
      }
    }
  }
}