In order to achieve this perform the steps below:

1. Open the project in Visual Studio
2. Open the Global.asax file
3. Subscribe to the Bootstrapper_Initialized event in the Application_Start()
    
   protected void Application_Start(object sender, EventArgs e)

           {

               Bootstrapper.Initialized += new EventHandler<Telerik.Sitefinity.Data.ExecutedEventArgs>(this.Bootstrapper_Initialized);

           }         

    
   
    
4. Subscribe to the IDataEvent in the Bootstrapper_Initialized handler
    
   protected void Bootstrapper_Initialized(object sender, Telerik.Sitefinity.Data.ExecutedEventArgs e)

           {

               if (e.CommandName == "Bootstrapped")

               {

                   EventHub.Subscribe<IDataEvent>(Content_Action);

               }

           }

            
5. Implement the Content_Action event handler with the custom logic that will be executed when a content block is created, edited or deleted.
   
   To do this check if the contentType.BaseType.FullName is Telerik.Sitefinity.GenericContent.Model.Content and then check the action (if it is "New", "Updated", "Deleted").
   
   Here is a sample code for your convenience:
   
    
   using System;

   using System.Collections.Generic;

   using System.Linq;

   using System.Web;

   using System.Web.Security;

   using System.Web.SessionState;

   using Telerik.Sitefinity.Abstractions;

   using Telerik.Sitefinity.Data;

   using Telerik.Sitefinity.Data.Events;

   using Telerik.Sitefinity.Services;

    

   namespace SitefinityWebApp

   {

       public class Global : System.Web.HttpApplication

       {

           protected void Application_Start(object sender, EventArgs e)

           {

               Bootstrapper.Initialized += new EventHandler<Telerik.Sitefinity.Data.ExecutedEventArgs>(this.Bootstrapper_Initialized);

           }

    

           protected void Bootstrapper_Initialized(object sender, Telerik.Sitefinity.Data.ExecutedEventArgs e)

           {

               if (e.CommandName == "Bootstrapped")

               {

                   EventHub.Subscribe<IDataEvent>(Content_Action);

               }

           }

    

           private void Content_Action(IDataEvent @event)

           {

               var action = @event.Action;

               var contentType = @event.ItemType;

    

               if (contentType.BaseType.FullName == "Telerik.Sitefinity.GenericContent.Model.Content")

               {

                   if (action == "New")

                   {

                       // execute your custom logic here when a content block is created                     

                   }

    

                   if (action == "Updated")

                   {

                       // execute your custom logic here when a content block is updated                   

                   }

    

                   if (action == "Deleted")

                   {

                       // execute your custom logic here when a content block is deleted                   

                   }

               }

           }

       }

   }

More information about the IDataEvent could be found on the following link from the Sitefinity documentation:

http://docs.sitefinity.com/for-developers-idataevent