public FeatureClass GetFeatureClass()

// Creates a new annotation template for the specified annotation layer.
await QueuedTask.Run(() =>
  {
    Inspector insp = null;
    // get the anno feature class
    var fc = annotationLayer.GetFeatureClass() as ArcGIS.Core.Data.Mapping.AnnotationFeatureClass;

    // get the feature class CIM definition which contains the labels, symbols
    var cimDefinition = fc.GetDefinition() as ArcGIS.Core.Data.Mapping.AnnotationFeatureClassDefinition;
    var labels = cimDefinition.GetLabelClassCollection();
    var symbols = cimDefinition.GetSymbolCollection();

    // make sure there are labels, symbols
    if (labels.Count == 0 || symbols.Count == 0)
      return;

    // find the label class required
    //   typically you would use a subtype name or some other characteristic
    // in this case lets just use the first one

    var label = labels[0];

    // each label has a textSymbol
    // the symbolName *should* be the symbolID to be used
    var symbolName = label.TextSymbol.SymbolName;
    int symbolID = -1;
    if (!int.TryParse(symbolName, out symbolID))
    {
      // int.TryParse fails - attempt to find the symbolName in the symbol collection
      foreach (var symbol in symbols)
      {
        if (symbol.Name == symbolName)
        {
          symbolID = symbol.ID;
          break;
        }
      }
    }
    // no symbol?
    if (symbolID == -1)
      return;

    // load the schema
    insp = new Inspector();
    insp.LoadSchema(annotationLayer);

    // ok to assign these fields using the inspector[fieldName] methodology
    //   these fields are guaranteed to exist in the annotation schema
    insp["AnnotationClassID"] = label.ID;
    insp["SymbolID"] = symbolID;

    // set up some additional annotation properties
    AnnotationProperties annoProperties = insp.GetAnnotationProperties();
    annoProperties.FontSize = 36;
    annoProperties.TextString = "My Annotation feature";
    annoProperties.VerticalAlignment = VerticalAlignment.Top;
    annoProperties.HorizontalAlignment = HorizontalAlignment.Justify;

    insp.SetAnnotationProperties(annoProperties);

    var tags = new[] { "Annotation", "tag1", "tag2" };

    // use daml-id rather than guid
    string defaultTool = "esri_editing_SketchStraightAnnoTool";

    // tool filter is the tools to filter OUT
    var toolFilter = new[] { "esri_editing_SketchCurvedAnnoTool" };

    // create a new template 
    var newTemplate = annotationLayer.CreateTemplate("new annotation template", "description", insp, defaultTool, tags, toolFilter);
  });

{
  //Must be called within QueuedTask.Run()
  void GetCount(FeatureLayer featureLayer)
  {
    // Row count in a Table
    Table table = featureLayer.GetTable();
    long count = table.GetCount();

    // Feature count in a FeatureClass
    FeatureLayer lyr = MapView.Active.Map.GetLayersAsFlattenedList().OfType<FeatureLayer>().FirstOrDefault();
    FeatureClass featureClass = lyr.GetFeatureClass();
    count = featureClass.GetCount();
  }
}