protected virtual Task<bool> OnSketchCompleteAsync( 
   Geometry geometry
)

//In your config.daml...set the categoryRefID
//<tool id="..." categoryRefID="esri_editing_construction_annotation" caption="Create Anno" ...>

//Sketch type Point or Line or BezierLine in the constructor...
public class ProSnippetAnnotationConstructionTool : MapTool
{
  public ProSnippetAnnotationConstructionTool()
  {
    IsSketchTool = true;
    UseSnapping = true;
    SketchType = SketchGeometryType.Point;
  }

  /// <summary>
  /// Handles the completion of a sketch operation and creates an annotation feature based on the provided geometry.
  /// </summary>
  protected async override Task<bool> OnSketchCompleteAsync(Geometry geometry)
  {
    if (CurrentTemplate == null || geometry == null)
      return false;
    // Create an edit operation
    var createOperation = new EditOperation
    {
      Name = string.Format("Create {0}", CurrentTemplate.Layer.Name),
      SelectNewFeatures = true
    };
    var insp = CurrentTemplate.Inspector;
    var result = await QueuedTask.Run(() =>
    {
      // get the annotation properties class
      AnnotationProperties annoProperties = insp.GetAnnotationProperties();
      // set custom annotation properties
      annoProperties.TextString = "my custom text";
      annoProperties.Color = ColorFactory.Instance.RedRGB;
      annoProperties.FontSize = 24;
      annoProperties.FontName = "Arial";
      annoProperties.HorizontalAlignment = HorizontalAlignment.Right;
      annoProperties.Shape = geometry;
      // assign annotation properties back to the inspector
      insp.SetAnnotationProperties(annoProperties);
      // Queue feature creation
      createOperation.Create(CurrentTemplate.Layer, insp);
      if (!createOperation.IsEmpty)
      {
        // Execute the operation
        return createOperation.Execute(); //Execute and ExecuteAsync will return true if the operation was successful and false if not
      }
      else
        return false;
    });
    return result;
  }
}

//Map Tool is used to perform Spatial selection.
//Graphic selection uses the selection geometry 
//to intersect the geometries of those elements (graphic or group) 
//that will be selected and then highlights them. 
{
  var selPoly = geometry as Polygon;
  // Note: must be called on the QueuedTask
  {
    //note: the selected elements may belong to more than one layer...
    var elems = MapView.Active.SelectElements(selPoly, SelectionCombinationMethod.New);
  }
}