ArcGIS Pro 3.2 API Reference Guide
ArcGIS.Core.CIM Namespace / CIMUniqueValueRenderer Class / ValueExpressionInfo Property
Example

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    ValueExpressionInfo Property (CIMUniqueValueRenderer)
    In This Topic
    Gets or sets ExpressionInfo that contains the Arcade expression that returns value as a string. When both Fields and ValueExpressionInfo are present ValueExpressionInfo is used.
    Syntax
    public CIMExpressionInfo ValueExpressionInfo {get; set;}
    Public Property ValueExpressionInfo As CIMExpressionInfo
    Example
    Evaluating Arcade Visual Variable Expressions on a Renderer
    //Consult https://github.com/Esri/arcade-expressions/ and
    //https://developers.arcgis.com/arcade/ for more examples
    //and arcade reference
    
    var mv = MapView.Active;
    var map = mv.Map;
    
    QueuedTask.Run(() =>
    {
      //Assume we a layer - Oregon County (poly) that is using Visual Variable
      //expressions that we want to evaluate interactively...
      var def = oregon_cnts.GetDefinition() as CIMFeatureLayer;
    
      //Most all feature renderers have a VisualVariable collection
      var renderer = def.Renderer as CIMUniqueValueRenderer;
      var vis_variables = renderer.VisualVariables?.ToList() ??
                            new List<CIMVisualVariable>();
      if (vis_variables.Count == 0)
        return;//there are none
      var vis_var_with_expr = new Dictionary<string, string>();
      //see if any are using expressions
      foreach (var vv in vis_variables)
      {
        if (vv is CIMColorVisualVariable cvv)
        {
          if (!string.IsNullOrEmpty(cvv.ValueExpressionInfo?.Expression))
            vis_var_with_expr.Add("Color", cvv.ValueExpressionInfo?.Expression);
        }
        else if (vv is CIMTransparencyVisualVariable tvv)
        {
          if (!string.IsNullOrEmpty(tvv.ValueExpressionInfo?.Expression))
            vis_var_with_expr.Add("Transparency", tvv.ValueExpressionInfo?.Expression);
        }
        else if (vv is CIMSizeVisualVariable svv)
        {
          if (!string.IsNullOrEmpty(svv.ValueExpressionInfo?.Expression))
            vis_var_with_expr.Add("Outline", svv.ValueExpressionInfo?.Expression);
        }
      }
      if (vis_var_with_expr.Count == 0)
        return;//there arent any with expressions
    
      //loop through the features (outer)
      //per feature evaluate each visual variable.... (inner)
      //....
      //the converse is to loop through the expressions (outer)
      //then per feature evaluate the expression (inner)
      using (var rc = oregon_cnts.Search())
      {
        while (rc.MoveNext())
        {
          foreach (var kvp in vis_var_with_expr)
          {
            var expr_info = new CIMExpressionInfo()
            {
              Expression = kvp.Value,
              ReturnType = ExpressionReturnType.Default
            };
            //per feature eval each expression...
            using (var arcade = ArcadeScriptEngine.Instance.CreateEvaluator(
                                        expr_info, ArcadeProfile.Visualization))
            {
    
              var variables = new List<KeyValuePair<string, object>>() {
                new KeyValuePair<string, object>("$feature", rc.Current)
              };
              //note 2D maps can also have view scale...
              //...if necessary...
              if (mv.ViewingMode == MapViewingMode.Map)
              {
                variables.Add(new KeyValuePair<string, object>(
                  "$view.scale", mv.Camera.Scale));
              }
              var result = arcade.Evaluate(variables).GetResult().ToString();
              //output
              System.Diagnostics.Debug.WriteLine(
                 $"[{rc.Current.GetObjectID()}] '{kvp.Key}': {result}");
            }
          }
        }
      }
    
      ////foreach (var kvp in vis_var_with_expr)
      ////{
      ////  var expr_info = new CIMExpressionInfo()
      ////  {
      ////    Expression = kvp.Value,
      ////    ReturnType = ExpressionReturnType.Default
      ////  };
    
      ////  using (var arcade = ArcadeScriptEngine.Instance.CreateEvaluator(
      ////                                  expr_info, ArcadeProfile.Visualization))
      ////  {
      ////    //loop through the features
      ////    using (var rc = oregon_cnts.Search())
      ////    {
      ////      while (rc.MoveNext())
      ////      {
      ////        var variables = new List<KeyValuePair<string, object>>() {
      ////          new KeyValuePair<string, object>("$feature", rc.Current)
      ////        };
    
      ////        var result = arcade.Evaluate(variables).GetResult();
      ////        //output
      ////        //...
      ////      }
      ////    }
      ////  }
      ////}
    });
    
    Modify renderer using Arcade
    var lyr = MapView.Active.Map.GetLayersAsFlattenedList().OfType<FeatureLayer>().FirstOrDefault(f => f.ShapeType == esriGeometryType.esriGeometryPolygon);
    if (lyr == null) return;
    QueuedTask.Run(() =>
    {
      // GetRenderer from Layer (assumes it is a unique value renderer)
      var uvRenderer = lyr.GetRenderer() as CIMUniqueValueRenderer;
      if (uvRenderer == null) return;
      //layer has STATE_NAME field
      //community sample Data\Admin\AdminSample.aprx
      string expression = "if ($view.scale > 21000000) { return $feature.STATE_NAME } else { return 'All' }";
      CIMExpressionInfo updatedExpressionInfo = new CIMExpressionInfo
      {
        Expression = expression,
        Title = "Custom" // can be any string used for UI purpose.
      };
      //set the renderer's expression
      uvRenderer.ValueExpressionInfo = updatedExpressionInfo;
    
      //SetRenderer on Layer
      lyr.SetRenderer(uvRenderer);
    });
    Requirements

    Target Platforms: Windows 11, Windows 10

    ArcGIS Pro version: 3 or higher.
    See Also