ArcGIS Pro 2.9 API Reference Guide
Subscribe Method (ActiveTemplateChangedEvent)
Example 

ArcGIS.Desktop.Editing.Events Namespace > ActiveTemplateChangedEvent Class : Subscribe Method
A delegate that is executed when the ActiveTemplateChangedEvent is published.
(optional) The type of reference used to maintain the delegate. false is a weak reference, true is a strong reference. (default value = false)
Subscribes to the ActiveTemplateChangedEvent.
Syntax

Parameters

action
A delegate that is executed when the ActiveTemplateChangedEvent is published.
keepSubscriberAlive
(optional) The type of reference used to maintain the delegate. false is a weak reference, true is a strong reference. (default value = false)

Return Value

A token that uniquely identifies the added subscription, and may subsequently be used with Unsubscribe.
Example
ArcGIS.Desktop.Editing.Events.ActiveTemplateChangedEvent.Subscribe(OnActiveTemplateChanged);

async void OnActiveTemplateChanged(ArcGIS.Desktop.Editing.Events.ActiveTemplateChangedEventArgs args)
{
  // return if incoming template is null
  if (args.IncomingTemplate == null)
    return;

  // Activate two-point line tool for Freeway template in the Layers map
  if (args.IncomingTemplate.Name == "Freeway" && args.IncomingMapView.Map.Name == "Layers")
    await args.IncomingTemplate.ActivateToolAsync("esri_editing_SketchTwoPointLineTool");
}
Requirements

Target Platforms: Windows 11, Windows 10, Windows 8.1

See Also

Reference

ActiveTemplateChangedEvent Class
ActiveTemplateChangedEvent Members