ProSnippets Labeling

Language:              C#  
Subject:               Labeling  
Contributor:           ArcGIS Pro SDK Team <[email protected]>  
Organization:          Esri, http://www.esri.com  
Date:                  11/7/2025  
ArcGIS Pro:            3.6  
Visual Studio:         2022  

Get the active map's labeling engine - Maplex or Standard labeling engine

// 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;
  }

Change the active map's labeling engine from Standard to Maplex or vice versa

// 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);
  }

Apply text symbol to a feature layer

// Note: call within QueuedTask.Run()
  {
    //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();
    //Set the label classes' symbol to the custom text symbol
    //Refer to the ProSnippets-TextSymbols wiki page for help with creating custom text symbols.
    //Example: var textSymbol = await CreateTextSymbolWithHaloAsync();
    theLabelClass.TextSymbol.Symbol = textSymbol;
    lyrDefn.LabelClasses = listLabelClasses.ToArray(); //Set the labelClasses back
    featureLayer.SetDefinition(lyrDefn); //set the layer's definition
                                         //set the label's visibility
    featureLayer.SetLabelVisibility(true);
  }

Enable labeling of a layer

// Note: call within QueuedTask.Run()
  {
    if (!featureLayer.IsLabelVisible)
      //set the label's visibility
      featureLayer.SetLabelVisibility(true);
  }

Modify the Placement/Position of labels - Point geometry

// Note: call within QueuedTask.Run()
  {
    //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 
    //Check if the label engine is Maplex or standard.
    CIMGeneralPlacementProperties labelEngine =
       MapView.Active.Map.GetDefinition().GeneralPlacementProperties;
    if (labelEngine is CIMStandardGeneralPlacementProperties) //Current labeling engine is Standard labeling engine               
      theLabelClass.StandardLabelPlacementProperties.PointPlacementMethod =
               StandardPointPlacementMethod.OnTopPoint;
    else    //Current labeling engine is Maplex labeling engine            
      theLabelClass.MaplexLabelPlacementProperties.PointPlacementMethod =
              MaplexPointPlacementMethod.CenteredOnPoint;

    lyrDefn.LabelClasses = listLabelClasses.ToArray(); //Set the labelClasses back
    featureLayer.SetDefinition(lyrDefn); //set the layer's definition
  }

Modify the Placement/Position of labels - Line geometry

// Note: call within QueuedTask.Run()
  {
    //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 
    //Check if the label engine is Maplex or standard.
    CIMGeneralPlacementProperties labelEngine =
        MapView.Active.Map.GetDefinition().GeneralPlacementProperties;
    if (labelEngine is CIMStandardGeneralPlacementProperties)
    {
      //Current labeling engine is Standard labeling engine
      var lineLablePosition = new CIMStandardLineLabelPosition
      {
        Perpendicular = true,
        Parallel = false,
        ProduceCurvedLabels = false,
        Horizontal = false,
        OnTop = true
      };
      theLabelClass.StandardLabelPlacementProperties.LineLabelPosition =
          lineLablePosition;
    }
    else //Current labeling engine is Maplex labeling engine
    {
      theLabelClass.MaplexLabelPlacementProperties.LinePlacementMethod =
                    MaplexLinePlacementMethod.CenteredPerpendicularOnLine;
      theLabelClass.MaplexLabelPlacementProperties.LineFeatureType =
                    MaplexLineFeatureType.General;
    }
    //theLabelClass.MaplexLabelPlacementProperties.LinePlacementMethod = MaplexLinePlacementMethod.CenteredPerpendicularOnLine;
    lyrDefn.LabelClasses = listLabelClasses.ToArray(); //Set the labelClasses back
    featureLayer.SetDefinition(lyrDefn); //set the layer's definition
  }

Modify the Placement/Position of labels - Polygon geometry

// Note: call within QueuedTask.Run()
  {
    //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 
    //Check if the label engine is Maplex or standard.
    CIMGeneralPlacementProperties labelEngine = MapView.Active.Map.GetDefinition().GeneralPlacementProperties;
    if (labelEngine is CIMStandardGeneralPlacementProperties)
    {
      //Current labeling engine is Standard Labeling engine
      theLabelClass.StandardLabelPlacementProperties.PolygonPlacementMethod =
               StandardPolygonPlacementMethod.AlwaysHorizontal;
      theLabelClass.StandardLabelPlacementProperties.PlaceOnlyInsidePolygon = true;
    }
    else
    {
      //Current labeling engine is Maplex labeling engine
      theLabelClass.MaplexLabelPlacementProperties.PolygonFeatureType =
                               MaplexPolygonFeatureType.LandParcel;
      theLabelClass.MaplexLabelPlacementProperties.AvoidPolygonHoles = true;
      theLabelClass.MaplexLabelPlacementProperties.PolygonPlacementMethod =
                          MaplexPolygonPlacementMethod.HorizontalInPolygon;
      theLabelClass.MaplexLabelPlacementProperties.CanPlaceLabelOutsidePolygon = true;
    }

    lyrDefn.LabelClasses = listLabelClasses.ToArray(); //Set the labelClasses back
    featureLayer.SetDefinition(lyrDefn); //set the layer's definition
                                         //set the label's visiblity
    featureLayer.SetLabelVisibility(true);
  }

Modify Orientation of a label using the MaplexEngine - Points and Polygon geometry

// Note: call within QueuedTask.Run()
  {
    //Check if the label engine is Maplex or standard.
    CIMGeneralPlacementProperties labelEngine = MapView.Active.Map.GetDefinition().GeneralPlacementProperties;
    if (labelEngine is CIMStandardGeneralPlacementProperties)
      return;

    //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 Orientation                 
    theLabelClass.MaplexLabelPlacementProperties.GraticuleAlignment = true;
    theLabelClass.MaplexLabelPlacementProperties.GraticuleAlignmentType = MaplexGraticuleAlignmentType.Curved;

    lyrDefn.LabelClasses = listLabelClasses.ToArray(); //Set the labelClasses back
    featureLayer.SetDefinition(lyrDefn); //set the layer's definition       
  }

Modify Orientation of a label using the MaplexEngine - Line geometry

// Note: call within QueuedTask.Run()
  {
    //Check if the label engine is Maplex or standard.
    CIMGeneralPlacementProperties labelEngine = MapView.Active.Map.GetDefinition().GeneralPlacementProperties;
    if (labelEngine is CIMStandardGeneralPlacementProperties)
      return;

    //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 Orientation
    theLabelClass.MaplexLabelPlacementProperties.AlignLabelToLineDirection = true;

    lyrDefn.LabelClasses = listLabelClasses.ToArray(); //Set the labelClasses back
    featureLayer.SetDefinition(lyrDefn); //set the layer's definition
  }

Modify label Rotation - Point geometry

// Note: call within QueuedTask.Run()
  {
    //Check if the label engine is Maplex or standard.
    CIMGeneralPlacementProperties labelEngine = MapView.Active.Map.GetDefinition().GeneralPlacementProperties;
    if (labelEngine is CIMStandardGeneralPlacementProperties)
      return;

    //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 Rotation
    CIMMaplexRotationProperties rotationProperties = new CIMMaplexRotationProperties
    {
      Enable = true, //Enable rotation
      RotationField = "ELEVATION", //Field that is used to define rotation angle
      AdditionalAngle = 15, //Additional rotation 
      RotationType = MaplexLabelRotationType.Arithmetic,
      AlignmentType = MaplexRotationAlignmentType.Perpendicular,
      AlignLabelToAngle = true
    };
    theLabelClass.MaplexLabelPlacementProperties.RotationProperties = rotationProperties;
    lyrDefn.LabelClasses = listLabelClasses.ToArray(); //Set the labelClasses back
    featureLayer.SetDefinition(lyrDefn); //set the layer's definition
  }

Spread labels across Polygon geometry

// Note: call within QueuedTask.Run()
  {
    //Check if the label engine is Maplex or standard.
    CIMGeneralPlacementProperties labelEngine = MapView.Active.Map.GetDefinition().GeneralPlacementProperties;
    if (labelEngine is CIMStandardGeneralPlacementProperties)
      return;

    //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();
    //Spread Labels (words and characters to fill feature)
    // Spread words to fill feature
    theLabelClass.MaplexLabelPlacementProperties.SpreadWords = true;
    //Spread Characters to a fixed limit of 50%
    theLabelClass.MaplexLabelPlacementProperties.SpreadCharacters = true;
    theLabelClass.MaplexLabelPlacementProperties.MaximumCharacterSpacing = 50.0;
    lyrDefn.LabelClasses = listLabelClasses.ToArray(); //Set the labelClasses back
    featureLayer.SetDefinition(lyrDefn); //set the layer's definition
  }

Modify label's Leader Line Anchor point properties - Polygon geometry

// Note: call within QueuedTask.Run()
  {
    //Check if the label engine is Maplex or standard.
    CIMGeneralPlacementProperties labelEngine = MapView.Active.Map.GetDefinition().GeneralPlacementProperties;
    if (labelEngine is CIMStandardGeneralPlacementProperties)
      return;

    //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();
    //If TextSymbol is a call-out the leader line anchor point can be modified
    theLabelClass.MaplexLabelPlacementProperties.PolygonAnchorPointType = MaplexAnchorPointType.Perimeter;
    lyrDefn.LabelClasses = [.. listLabelClasses]; //Set the labelClasses back
    featureLayer.SetDefinition(lyrDefn); //set the layer's definition
  }