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

public void CreateFeatureLinkedAnnotationFeatureClass(Geodatabase geodatabase, SpatialReference spatialReference)
{
  // Creating a feature-linked annotation feature class between water pipe and valve in water distribution network
  // with following user defined fields
  // PipeName 
  // GlobalID

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

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

  // Create a list of all field descriptions
  List<FieldDescription> fieldDescriptions = new List<FieldDescription> { pipeGlobalID, 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 = 255,
      G = 0,
      B = 0,
      Alpha = 0.5f
    }
  };

  // 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 linked feature description
  // Linked feature class name
  string linkedFeatureClassName = "WaterPipe";

  // Create fields for water pipe
  FieldDescription waterPipeGlobalID = FieldDescription.CreateGlobalIDField();
  FieldDescription pipeName = FieldDescription.CreateStringField("PipeName", 255);

  // Create a list of water pipe field descriptions
  List<FieldDescription> pipeFieldDescriptions = new List<FieldDescription> { waterPipeGlobalID, pipeName };

  // Create a linked feature class description
  FeatureClassDescription linkedFeatureClassDescription = new FeatureClassDescription(linkedFeatureClassName, pipeFieldDescriptions,
    new ShapeDescription(GeometryType.Polyline, spatialReference));

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

  // Add the creation of the linked feature class to the list of DDL tasks
  FeatureClassToken linkedFeatureClassToken = schemaBuilder.Create(linkedFeatureClassDescription);

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

  // Add the creation of the 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.
  }
}

public static void CreateDictionary()
{
  //Get the map's defintion
  var mapDefn = MapView.Active.Map.GetDefinition();
  //Get the Map's Maplex labelling engine properties
  var mapDefnPlacementProps = mapDefn.GeneralPlacementProperties as CIMMaplexGeneralPlacementProperties;

  //Define the abbreaviations we need in an array            
  List<CIMMaplexDictionaryEntry> abbreviationDictionary = new List<CIMMaplexDictionaryEntry>
        {
            new CIMMaplexDictionaryEntry {
            Abbreviation = "Hts",
            Text = "Heights",
            MaplexAbbreviationType = MaplexAbbreviationType.Ending

         },
            new CIMMaplexDictionaryEntry
            {
                Abbreviation = "Ct",
                Text = "Text",
                MaplexAbbreviationType = MaplexAbbreviationType.Ending

            }
            //etc
        };
  //The Maplex Dictionary - can hold multiple Abbreviation collections
  var maplexDictionary = new List<CIMMaplexDictionary>
        {
            new CIMMaplexDictionary {
                Name = "NameEndingsAbbreviations",
                MaplexDictionary = abbreviationDictionary.ToArray()
            }

        };
  //Set the Maplex Label Engine Dictionary property to the Maplex Dictionary collection created above.
  mapDefnPlacementProps.Dictionaries = maplexDictionary.ToArray();
  //Set the Map defintion 
  MapView.Active.Map.SetDefinition(mapDefn);
}

private static void ApplyDictionary()
{
  var featureLayer = MapView.Active.Map.GetLayersAsFlattenedList().OfType<FeatureLayer>().First();

  QueuedTask.Run(() =>
  {
    //Creates Abbreviation dictionary and adds to Map Defintion                                
    CreateDictionary();
    //Get the layer's definition
    var lyrDefn = featureLayer.GetDefinition() as CIMFeatureLayer;
    //Get the label classes - we need the first one
    var listLabelClasses = lyrDefn.LabelClasses.ToList();
    var theLabelClass = listLabelClasses.FirstOrDefault();
    //Modify label Placement props to use abbreviation dictionary 
    CIMGeneralPlacementProperties labelEngine = MapView.Active.Map.GetDefinition().GeneralPlacementProperties;
    theLabelClass.MaplexLabelPlacementProperties.DictionaryName = "NameEndingsAbbreviations";
    theLabelClass.MaplexLabelPlacementProperties.CanAbbreviateLabel = true;
    theLabelClass.MaplexLabelPlacementProperties.CanStackLabel = false;
    //Set the labelClasses back
    lyrDefn.LabelClasses = listLabelClasses.ToArray();
    //set the layer's definition
    featureLayer.SetDefinition(lyrDefn);
  });
}

//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);