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

/// <summary>
/// Creates a solid fill background text symbol with an Accent bar and leader line.  The [CIMBackgroundCallout](https://pro.arcgis.com/en/pro-app/sdk/api-reference/#topic474.html) created has a solid fill aqua polygon, with a black dash-dot-dash leader line and a solid accent bar.
/// ![lineCallOut](https://ArcGIS.github.io/arcgis-pro-sdk/images/Labeling//background-callout.png)
/// </summary>
{
  //Note: Run this code inside a QueuedTask
  var textSymbolBackgroundCallout = SymbolFactory.Instance.ConstructTextSymbol(ColorFactory.Instance.BlackRGB, 8, "Tahoma", "Bold");
  //Create a call out
  var backgroundCalloutSymbol = new CIMBackgroundCallout();
  //Leader line
  //Get a line symbol
  var lineSymbol = SymbolFactory.Instance.ConstructLineSymbol(ColorFactory.Instance.BlackRGB, 1, SimpleLineStyle.DashDotDot);
  //Create a solid fill polygon symbol for the callout.
  var aquaBackground = ColorFactory.Instance.CreateRGBColor(190, 255, 232, 100);
  var polySymbol = SymbolFactory.Instance.ConstructPolygonSymbol(aquaBackground, SimpleFillStyle.Solid);
  //assign the line to the callout
  backgroundCalloutSymbol.LeaderLineSymbol = lineSymbol;
  //Offset for the text
  textSymbolBackgroundCallout.OffsetX = 10;
  textSymbolBackgroundCallout.OffsetY = 10;
  //Assign the polygon to the background callout
  backgroundCalloutSymbol.BackgroundSymbol = polySymbol;
  //Accent bar
  var accentSymbol = SymbolFactory.Instance.ConstructLineSymbol(ColorFactory.Instance.BlackRGB, 2, SimpleLineStyle.Solid);
  backgroundCalloutSymbol.AccentBarSymbol = accentSymbol;
  //Set margins for the callout
  backgroundCalloutSymbol.Margin = new CIMTextMargin
  {
    Left = 5,
    Right = 5,
    Top = 5,
    Bottom = 5
  };

  //assign the callout to the textSymbol
  textSymbolBackgroundCallout.Callout = backgroundCalloutSymbol;
  //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
}