Extending Umbraco with Event Handlers

Before you start, I recommend taking a look at this page, it'll explain most of the things you need to know about what each event handler does.

To create a custom event handler, you need to create a new class in your website and extend from ApplicationEventHandler:

using Umbraco.Core;
using Umbraco.Core.Events;
using Umbraco.Core.Models;
using Umbraco.Core.Publishing;
using Umbraco.Core.Services;

namespace My.Namespace
{
    public class MyEventHandler : ApplicationEventHandler
    {
    }
}

The class will automatically loaed into your websie when it starts, but before u can put it to use, you need to add a few extra methods:

using Umbraco.Core;
using Umbraco.Core.Events;
using Umbraco.Core.Models;
using Umbraco.Core.Publishing;
using Umbraco.Core.Services;

namespace My.Namespace
{
    public class MyEventHandler : ApplicationEventHandler
    {
        public MyEventHandler()
        {
            
        }

        public void OnApplicationInitialized(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
        { }

        public void OnApplicationStarting(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
        { }

        public void OnApplicationStarted(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
        { }
    }
}

Then you can add your event handlers:

using Umbraco.Core;
using Umbraco.Core.Events;
using Umbraco.Core.Models;
using Umbraco.Core.Publishing;
using Umbraco.Core.Services;

namespace My.Namespace
{
    public class MyEventHandler : ApplicationEventHandler
    {
        public MyEventHandler()
        {
            ContentService.Trashing += Document_Trash;
        }

        private void Document_Trash(IContentService sender, MoveEventArgs e)
        {
            // Perform action here when node is sent to trash
        }

        public void OnApplicationInitialized(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
        { }

        public void OnApplicationStarting(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
        { }

        public void OnApplicationStarted(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
        { }
    }
}

And thats it! You can add more event handlers if needed, and you're using Visual Studio, you can see what each devent handler requires by browsing to their definition.