Synchronize Site list with Subsite list via Event Receivers on SharePoint 2013 

Synchronizing a child list with a Parent list can be done by writing the event receivers. Whenever a user will add, update or delete operations on a parent list then the child will also be synchronized accordingly. The following are the series of steps that you need to know to accomplish it;

The Parent list resides in the root site of Site collection. Child List is part of a sub site  The following is how my parent and child list looks like in my environment;

              

For writing event receivers  create an empty SharePoint 2013 project in Visual Studio 2012. In the project, select add new item and select Event Receiver as shown in the figure below.

Select the type of event receiver you need to add. In my case, I selected a Custom List for the time being. I will show you later how to change it.

Now once the event is generated, go to the Elements.xml of the Event reciever and replace the "ListTemplateId=100" with ListUrl="Lists\ParentList". Here my List name is 'ParentList'. Now the event receivers will be going to be attach with ParentList once they are deployed.

Go to the .cs file of your event reciever and write the following code to automate the synchronization.

/// 

        /// An item was added.
        /// 
        public override void ItemAdded(SPItemEventProperties properties)
        {
            SPWeb _currentweb = properties.Web;
            string strSiteCollct = _currentweb.Site.Url;

            using (SPWeb _subSite = _currentweb.Webs[0])
            {
                SPList _list = _subSite.Lists["ChildList"];
                SPListItem _item = _list.AddItem();
                _item[SPBuiltInFieldId.ID] = properties.ListItemId;
                _item["Title"] = properties.ListItem["Title"].ToString();
                _item["Employee Name"] = properties.ListItem["Employee Name"].ToString();
                _item["Joining Date"] = properties.ListItem["Joining Date"].ToString();

                _item.Update();
            }
            base.ItemAdded(properties);
        }

        /// 

        /// An item was updated.
        /// 
        public override void ItemUpdated(SPItemEventProperties properties)
        {
            SPWeb _currentweb = properties.Web;
            using (SPWeb _subSite = _currentweb.Webs[0])
            {
                SPList _list = _subSite.Lists["ChildList"];

                int ItemId = properties.ListItemId;
                SPListItem _item = _list.GetItemById(ItemId);

                _item["Title"] = properties.ListItem["Title"].ToString();
                _item["Employee Name"] = properties.ListItem["Employee Name"].ToString();
                _item["Joining Date"] = properties.ListItem["Joining Date"].ToString();
                _item.Update();
            }
            base.ItemUpdated(properties);
        }

        /// 

        /// An item was deleted.
        /// 
        public override void ItemDeleted(SPItemEventProperties properties)
        {
            SPWeb _currentweb = properties.Web;
            using (SPWeb _subSite = _currentweb.Webs[0])
            {
                SPList _list = _subSite.Lists["ChildList"];

                int ItemId = properties.ListItemId;
                if (DoesListItemExist(_list, ItemId)) // Before deleting item verify, it exist in the ChildList
                {
                    SPListItem _item = _list.GetItemById(ItemId);
                    _item.Delete(); //Delete item
                    _list.Update();
                }                
            }

            base.ItemDeleted(properties);
        }

        private Boolean DoesListItemExist(SPList _list, int ListID)
        {
            try
            {
                SPQuery query = new SPQuery();
                string strQuery = string.Format(@"
                                            
                                                 
                                                    
                                                    {0}
                                                
                                            ", ListID);
                query.Query = strQuery;
                SPListItemCollection found = _list.GetItems(query);
                if (found.Count > 0)
                {
                    return true;
                }

                return false;
            }
            catch (Exception)
            {

                throw;
            }

        }

That's it...deploy the event receiver and perform add, update and delete operations on your parent list. The changes will also be reflected on the child list of the subsite. ..:)