WebExtensions.cs

using System.Linq.Expressions;
using Microsoft.SharePoint.Client;
using System;
using System.Collections.Generic;
using System.Linq;

namespace SharePoint.Client.Extensions
{
    public static class WebExtensions
    {
        /// <summary>
        /// Retrieve list data from site collection 
        /// </summary>
        /// <param name="parentWeb"></param>
        /// <param name="serverTemplateId">List Template Id</param>
        /// <param name="query">CAML Query</param>
        /// <returns></returns>
        public static List<ListDataResult> GetSiteData(this Web parentWeb, int serverTemplateId, CamlQuery query)
        {
            var results = new List<ListDataResult>();
            GetSiteData(parentWeb, serverTemplateId, query, ref results);
            return results;
        }



        private static void GetSiteData(this Web parentWeb, int serverTemplateId, CamlQuery query, ref List<ListDataResult> results)
        {
            Expression<Func<Web, object>>[] expr = { w => w.Lists.Where(l => l.BaseTemplate == serverTemplateId), w => w.Id}; 
            var ctx = parentWeb.Context;
            var qry = new SubwebQuery();
            var subWebs = parentWeb.GetSubwebsForCurrentUser(qry);
            ctx.Load(parentWeb, expr);
            ctx.Load(subWebs,wcol => wcol.Include(expr));
            ctx.ExecuteQuery();
            if (results.Count == 0)
                RetrieveAndProcessListsResults(results,parentWeb,query);
            if (subWebs.Count > 0)
            {
                foreach (var web in subWebs)
                {
                    RetrieveAndProcessListsResults(results, web, query);
                    GetSiteData(web,serverTemplateId,query,ref results);
                }
            }
        }


        private static void RetrieveAndProcessListsResults(List<ListDataResult> results, Web web, CamlQuery query)
        {
            var allItems = new Dictionary<List,ListItemCollection>();
            var ctx = web.Context;
            foreach (var list in web.Lists)
            {
                var items = list.GetItems(query);
                ctx.Load(list, l => l.Fields, l => l.Id);
                ctx.Load(items);
                allItems[list] = items;
            }
            ctx.ExecuteQuery();
            foreach (var items in allItems)
            {
                var result = new ListDataResult();
                result.WebId = web.Id;
                result.ListId = items.Key.Id;
                result.Data = items.Value.Select(v => v.FieldValues).ToList();
                results.Add(result);
            }
        }

    }

    public class ListDataResult
    {
        public Guid WebId { get; set; }

        public Guid ListId { get; set; }

        public List<Dictionary<string,object>> Data { get; set; }
    }
}