EventContext

Open Nop solution. Add a new DLL project. Right click on that project in solution explorer and add a reference to the business logic DLL project.

Right click on the NopCommerceStore project in solution explorer and add a reference to the new DLL project.

Open up EventContext.cs in the business logic DLL and see which event you want to use.

In the new DLL add a static class with a static function to handle the event. Example:

public static class FleetObserverLiteNopCommercePlugin
    {
        /// <summary>
        /// OrderPlaced event handler
        /// </summary>
        /// <remarks>Needs to be threadsafe</remarks>
        public static void OrderPaidHandler(object sender, OrderEventArgs e)
        {
                .... do stuff
        }

Attach the event in global.asax:
      
    void Application_BeginRequest(object sender, EventArgs e)
    {
        NopConfig.Init();
        if (!InstallerHelper.ConnectionStringIsSet())
        {
            InstallerHelper.RedirectToInstallationPage();
        }

        EventContext.Current.OrderPaid += FleetObserverLiteNopCommercePlugin.OrderPaidHandler;
    }

Test.