public abstract class CIMGeneralPlacementProperties : CIMObject, System.ComponentModel.INotifyPropertyChanged, System.Xml.Serialization.IXmlSerializable  

{
  // Must be called within QueuedTask.Run
  void CreateStandAloneAnnotationFeatureClass(
    Geodatabase geodatabase, SpatialReference spatialReference)
  {
    // Creating a Cities annotation feature class
    // with following user defined fields
    // Name 
    // GlobalID

    // Annotation feature class name
    string annotationFeatureClassName = "CitiesAnnotation";

    // Create user defined attribute fields for annotation feature class 
    FieldDescription globalIDFieldDescription = FieldDescription.CreateGlobalIDField();
    FieldDescription nameFieldDescription = FieldDescription.CreateStringField("Name", 255);

    // Create a list of all field descriptions
    List<FieldDescription> fieldDescriptions = new List<FieldDescription>
        { globalIDFieldDescription, nameFieldDescription };

    // Create a ShapeDescription object
    ShapeDescription shapeDescription = new ShapeDescription(GeometryType.Polygon, spatialReference);

    // Create general placement properties for Maplex engine 
    CIMMaplexGeneralPlacementProperties generalPlacementProperties =
      new CIMMaplexGeneralPlacementProperties
      {
        AllowBorderOverlap = true,
        PlacementQuality = MaplexQualityType.High,
        DrawUnplacedLabels = true,
        InvertedLabelTolerance = 1.0,
        RotateLabelWithDisplay = true,
        UnplacedLabelColor = new CIMRGBColor
        {
          R = 0,
          G = 255,
          B = 0,
          Alpha = 0.5f // Green
        }
      };

    // Create general placement properties for Standard engine

    //CIMStandardGeneralPlacementProperties generalPlacementProperties =
    //  new CIMStandardGeneralPlacementProperties
    //  {
    //    DrawUnplacedLabels = true,
    //    InvertedLabelTolerance = 3.0,
    //    RotateLabelWithDisplay = true,
    //    UnplacedLabelColor = new CIMRGBColor
    //    {
    //      R = 255, G = 0, B = 0, Alpha = 0.5f // Red
    //    } 
    //   };


    // Create annotation  label classes
    // Green label
    CIMLabelClass greenLabelClass = new CIMLabelClass
    {
      Name = "Green",
      ExpressionTitle = "Expression-Green",
      ExpressionEngine = LabelExpressionEngine.Arcade,
      Expression = "$feature.OBJECTID",
      ID = 1,
      Priority = 0,
      Visibility = true,
      TextSymbol = new CIMSymbolReference
      {
        Symbol = new CIMTextSymbol()
        {
          Angle = 45,
          FontType = FontType.Type1,
          FontFamilyName = "Tahoma",
          FontEffects = FontEffects.Normal,
          HaloSize = 2.0,

          Symbol = new CIMPolygonSymbol
          {
            SymbolLayers = new CIMSymbolLayer[]
            {
                new CIMSolidFill
                {
                  Color = CIMColor.CreateRGBColor(0, 255, 0)
                }
            },
            UseRealWorldSymbolSizes = true
          }
        },
        MaxScale = 0,
        MinScale = 0,
        SymbolName = "TextSymbol-Green"
      },
      StandardLabelPlacementProperties = new CIMStandardLabelPlacementProperties
      {
        AllowOverlappingLabels = true,
        LineOffset = 1.0
      },
      MaplexLabelPlacementProperties = new CIMMaplexLabelPlacementProperties
      {
        AlignLabelToLineDirection = true,
        AvoidPolygonHoles = true
      }
    };

    // Blue label
    CIMLabelClass blueLabelClass = new CIMLabelClass
    {
      Name = "Blue",
      ExpressionTitle = "Expression-Blue",
      ExpressionEngine = LabelExpressionEngine.Arcade,
      Expression = "$feature.OBJECTID",
      ID = 2,
      Priority = 0,
      Visibility = true,
      TextSymbol = new CIMSymbolReference
      {
        Symbol = new CIMTextSymbol()
        {
          Angle = 45,
          FontType = FontType.Type1,
          FontFamilyName = "Consolas",
          FontEffects = FontEffects.Normal,
          HaloSize = 2.0,

          Symbol = new CIMPolygonSymbol
          {
            SymbolLayers = new CIMSymbolLayer[]
            {
                new CIMSolidFill
                {
                  Color = CIMColor.CreateRGBColor(0, 0, 255)
                }
            },
            UseRealWorldSymbolSizes = true
          }
        },
        MaxScale = 0,
        MinScale = 0,
        SymbolName = "TextSymbol-Blue"
      },
      StandardLabelPlacementProperties = new CIMStandardLabelPlacementProperties
      {
        AllowOverlappingLabels = true,
        LineOffset = 1.0
      },
      MaplexLabelPlacementProperties = new CIMMaplexLabelPlacementProperties
      {
        AlignLabelToLineDirection = true,
        AvoidPolygonHoles = true
      }
    };

    // Create a list of labels
    List<CIMLabelClass> labelClasses = new List<CIMLabelClass> { greenLabelClass, blueLabelClass };

    // Create an annotation feature class description object to describe the feature class to create
    AnnotationFeatureClassDescription annotationFeatureClassDescription =
      new AnnotationFeatureClassDescription(annotationFeatureClassName, fieldDescriptions, shapeDescription,
        generalPlacementProperties, labelClasses)
      {
        IsAutoCreate = true,
        IsSymbolIDRequired = false,
        IsUpdatedOnShapeChange = true
      };

    // Create a SchemaBuilder object
    SchemaBuilder schemaBuilder = new SchemaBuilder(geodatabase);

    // Add the creation of the Cities annotation feature class to the list of DDL tasks
    schemaBuilder.Create(annotationFeatureClassDescription);

    // Execute the DDL
    bool success = schemaBuilder.Build();

    // Inspect error messages
    if (!success)
    {
      IReadOnlyList<string> errorMessages = schemaBuilder.ErrorMessages;
      //etc.
    }
  }
}

{
  // Note: call within QueuedTask.Run()
  {
    //Get the active map's definition - CIMMap.
    var cimMap = MapView.Active.Map.GetDefinition();
    //Get the labeling engine from the map definition
    CIMGeneralPlacementProperties labelEngine = cimMap.GeneralPlacementProperties;
  }
}

{
  // Note: call within QueuedTask.Run()
  {
    //Get the active map's definition - CIMMap.
    var cimMap = MapView.Active.Map.GetDefinition();
    //Get the labeling engine from the map definition
    var cimGeneralPlacement = cimMap.GeneralPlacementProperties;

    if (cimGeneralPlacement is CIMMaplexGeneralPlacementProperties)
    {
      //Current labeling engine is Maplex labeling engine
      //Create a new standard label engine properties
      var cimStandardPlacementProperties = new CIMStandardGeneralPlacementProperties();
      //Set the CIMMap's GeneralPlacementProperties to the new label engine
      cimMap.GeneralPlacementProperties = cimStandardPlacementProperties;
    }
    else
    {
      //Current labeling engine is Standard labeling engine
      //Create a new Maplex label engine properties
      var cimMaplexGeneralPlacementProperties = new CIMMaplexGeneralPlacementProperties();
      //Set the CIMMap's GeneralPlacementProperties to the new label engine
      cimMap.GeneralPlacementProperties = cimMaplexGeneralPlacementProperties;
    }
    //Set the map's definition
    MapView.Active.Map.SetDefinition(cimMap);
  }
}