MongoDB C＃ - 如何执行以下操作

Question

如何使用MongoDB和.NET的C＃驱动程序执行以下操作。

说我有以下的集合（忽略是否有语法错误）：

{_id: "2312321321sdd", "Ticker": "AAPL", "CompanyName" : "APPLE", "Viewed": "2013-05-13"} 
{_id: "2312321321sde", "Ticker": "AAPL", "CompanyName" : "APPLE", "Viewed": "2013-05-12"} 
{_id: "2312321321sdf", "Ticker": "GOOG", "CompanyName" : "GOOGLE", "Viewed": "2013-05-12"} 
{_id: "2312321321sdg", "Ticker": "MSFT", "CompanyName" : "MICROSOFT", "Viewed": "2013-05-12"} 
{_id: "2312321321sdh", "Ticker": "MSFT", "CompanyName" : "MICROSOFT", "Viewed": "2013-05-11"} 

使用C＃和/或LINQ与MongoDB的驱动程序，我该如何获得最新的3浏览过的商品，但也DISTINCT作为好吧，所以同一个TICKER没有双重的起伏。因此，最好在下面将得到恢复：提前

{_id: "2312321321sdd", "Ticker": "AAPL", "CompanyName" : "APPLE", "Viewed": "2013-05-13"} 
{_id: "2312321321sdf", "Ticker": "GOOG", "CompanyName" : "GOOGLE", "Viewed": "2013-05-12"} 
{_id: "2312321321sdg", "Ticker": "MSFT", "CompanyName" : "MICROSOFT", "Viewed": "2013-05-12"} 

感谢....

Answer 1

我不能说这一点无论使用LINQ甚至很多C＃，但它是你在MongoDB中C＃之后是什么就像今天一样。不幸的是，Collection.AsQueryable()不会让你走得更远。

聚合框架或MapReduce是要走的路。一组不同的代码需要适度，但这里是AF：

using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Text; 
using System.Threading.Tasks; 
using MongoDB.Bson; 
using MongoDB.Driver; 
using MongoDB.Driver.Linq; 

namespace ConsoleApplication1 
{ 
    class Program 
    { 
     static void Main(string[] args) 
     { 
      MongoCollection<Tick> coll = 
       new MongoClient("mongodb://11.11.11.11/test").GetServer() 
                   .GetDatabase("test") 
                   .GetCollection<Tick>("tix"); 

      var group = new BsonDocument 
       { 
        { 
         "$group", 
         new BsonDocument 
          { 
           { 
            "_id", "$CompanyName" 
           }, 
           { 
            "LastViewed", new BsonDocument 
             { 
              { 
               "$max", "$Viewed" 
              } 
             } 
           } 
          } 
        } 
       }; 

      foreach (
       var t in 
        coll.Aggregate(group, 
            new BsonDocument("$sort", new BsonDocument("LastViewed", -1)), 
            new BsonDocument("$limit", 3)) 
         .ResultDocuments) 
      { 
       Console.WriteLine("{0} last viewed {1}", t["_id"], t["LastViewed"]); 
      } 
    } 

    public class Tick 
    { 
     public string Id { get; set; } 
     public string Ticker { get; set; } 
     public string CompanyName { get; set; } 
     public string Viewed { get; set; } 
    } 
}