ExecutionEvents
Communication bridge between Dynamo and client libraries to notify
            about changes to execution state
            
using Dynamo.Session;
namespace Dynamo.Events
{
    public static class ExecutionEvents
    {
        public static IExecutionSession ActiveSession { get; set; }
        public static event ExecutionStateHandler GraphPreExecution;
        public static event ExecutionStateHandler GraphPostExecution;
        internal static void OnGraphPreExecution(IExecutionSession session)
        {
            ActiveSession = session;
            if (ExecutionEvents.GraphPreExecution != null)
                ExecutionEvents.GraphPreExecution(session);
        }
        internal static void OnGraphPostExecution(IExecutionSession session)
        {
            ActiveSession = null;
            if (ExecutionEvents.GraphPostExecution != null)
                ExecutionEvents.GraphPostExecution(session);
        }
    }
}