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

{
  // Must be called within QueuedTask.Run
  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.
    }
  }
}

{
    //Get the map's definition
    //Note: needs to be called on the MCT
    var mapDefn = MapView.Active.Map.GetDefinition();
    //Get the Map's Maplex labelling engine properties
    var mapDefnPlacementProps = mapDefn.GeneralPlacementProperties as CIMMaplexGeneralPlacementProperties;

    //Define the abbreviations 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 definition 
    MapView.Active.Map.SetDefinition(mapDefn);
}

{
    //Creates Abbreviation dictionary and adds to Map Definition                                
    //Refer to the " Create Abbreviation Dictionary in the Map Definition to a layer" snippet above
    //Get the layer's definition
    //Note: needs to be called on the MCT
    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;
    //Get the dictionary from the map definition
    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);
  }
}