public class CIMPointSymbolCallout : CIMLineCallout, System.ComponentModel.INotifyPropertyChanged, System.Xml.Serialization.IXmlSerializable  

/// <summary>
/// Creates a highway shield callout text symbol. The [CIMPointSymbolCallout](https://pro.arcgis.com/en/pro-app/sdk/api-reference/#topic4116.html) created is a highway shield point symbol from the ArcGIS 2D style.
/// ![lineCallOut](https://ArcGIS.github.io/arcgis-pro-sdk/images/Labeling/highway-callout.png)
/// </summary>
{
  //create a text symbol
  //Note: Run this code inside a QueuedTask
  var textSymbolPointCallout = SymbolFactory.Instance.ConstructTextSymbol(ColorFactory.Instance.WhiteRGB, 6, "Tahoma", "Bold");
  //Create a call out
  var shieldCalloutSymbol = new CIMPointSymbolCallout();
  //Get a Shield symbolStyleItem from ArcGIS 2D StyleProjectitem
  var symbolStyleItem = GetPointSymbol("ArcGIS 2D", "Shield 1");
  //assign the point symbol (Highway shield) to the callout
  shieldCalloutSymbol.PointSymbol = symbolStyleItem.Symbol as CIMPointSymbol;
  shieldCalloutSymbol.PointSymbol.SetSize(18.0); //set symbol size
                                                 //Assign the callout to the text symbol
  textSymbolPointCallout.Callout = shieldCalloutSymbol;
  //Refer to the snippet "How to apply a Text Symbol to labels of a layer" below to see how to apply this text symbol to a label class

  //Gets a Highway point symbol from a style
  static SymbolStyleItem GetPointSymbol(string styleProjectItemName, string symbolStyleName)
  {
    var style2DProjectItem = Project.Current.GetItems<StyleProjectItem>().Where(p => p.Name == styleProjectItemName).FirstOrDefault();
    var symbolStyle = style2DProjectItem.SearchSymbols(StyleItemType.PointSymbol, symbolStyleName).FirstOrDefault();
    return symbolStyle;
  }
}