如何使用 BsonDocument C# .NET 驅動程序在 MongoDB 中將多個投影和查找作為聚合執行？

Question

我無法通過 C# .NET 驅動程序使用聚合功能來執行多個投影和查找。

這里我需要使用 mongodb C# .NET 驅動程序復制查詢。

db.organizations.aggregate([
  {
    "$project": {
      "_id": {
        "$toString": "$_id"
      },
      "Name": "$Name",
      "LastDateUploaded": "$LastDateUploaded",
      "LastDateEvaluated": "$LastDateEvaluated",
      "PriorityId": "$PriorityId"
    }
  },
  {
    "$lookup": {
      "from": "workflows",
      "localField": "_id",
      "foreignField": "Data.OrganizationId",
      "as": "RelatedWorkflows"
    }
  },
  {
    "$lookup": {
      "from": "priorities",
      "localField": "PriorityId",
      "foreignField": "_id",
      "as": "Priority"
    }
  },
  {
    "$unwind": "$Priority"
  },
  {
    "$project": {
      "Name": "$Name",
      "WorkflowCounter": {
        "$size": "$RelatedWorkflows"
      },
      "LastDateUploaded": "$LastDateUploaded",
      "LastDateEvaluated": "$LastDateEvaluated",
      "Priority": "$Priority.Value"
    }
  },
  {
    "$sort": {
      "Priority": -1,
      "WorkflowCounter": 1,
      "LastDateUploaded": -1,
      "LastDateEvaluated": -1
    }
  }
])

我試圖做這樣的事情：

public class Organization
    {
        [BsonId]
        [BsonRepresentation(BsonType.ObjectId)]
        public string Id {get; set;}
        public string NPOId { get; set; }
        public string Name { get; set; }
        public string Address { get; set; }
        [BsonRepresentation(BsonType.ObjectId)]
        public string PriorityId { get; set; }
        [BsonIgnoreIfDefault]
        public Priority Priority { get; set; }
        public string City { get; set; }
        public string County { get; set; }
        [MaxLength(2)]
        public string State { get; set; }
        [BsonRepresentation(BsonType.ObjectId)]
        public string CountryId { get; set; }
        [BsonIgnoreIfDefault]
        public Country Country { get; set; }
        [MaxLength(5)]
        public string Zip { get; set; }
        public string TaxCode { get; set; }
        public string ParentTaxCode { get; set; }
        [BsonRepresentation(BsonType.ObjectId)]
        public string CharityTypeId { get; set; }
        [BsonRepresentation(BsonType.ObjectId)]
        public string PreferredExtractorId { get; set; }
        [BsonIgnoreIfDefault]
        public User PreferredExtractor{ get; set; }
        [BsonIgnoreIfDefault]
        public CharityType CharityType { get; set; }
        public string URL { get; set; }
        public decimal Revenue { get; set; }
        public decimal Expenses { get; set; }
        public decimal Assets { get; set; }
        public decimal Excess { get; set; }
        public string IRSType { get; set; }
        public string ICPAScore { get; set; }
        public string ICPBScore { get; set; }
        public string[] DefaultRules { get; set; }
        [BsonIgnore]
        public long NumberOfWorkflows { get; set; }
        public DateTime? LastDateUploaded { get; set; }
        public DateTime? LastDateEvaluated { get; set; }
    }

var organizations = db.GetCollection<Organization>("catalog.organizations");
            var aggregation = organizations.Aggregate().Match(_ => true);

            var projectionOne = new BsonDocument {
                { "$project", new BsonDocument { { "_id", new BsonDocument { { "$toString", "$_id" } } } } },
                { "Name", "$Name"},
                { "LastDateUploaded", "$LastDateUploaded" },
                { "LastDateEvaluated", "$LastDateEvaluated"},
                { "PriorityId", "$PriorityId"}
            };

            aggregation.Project(projectionOne);

            aggregation.AppendStage<Organizations>(new BsonDocument {
                { "$lookup", new BsonDocument { { "from", "wcf.workflows" }, { "localField", "_id" }, { "foreignField", "Data.OrganizationId" }, { "as", "RelatedWorkflows" } } }
            });

            aggregation.AppendStage<Organizations>(new BsonDocument {
                { "$lookup", new BsonDocument { { "from", "catalog.priorities" }, { "localField", "PriorityId" }, { "foreignField", "_id" }, { "as", "Priority" } } }
            });

            aggregation.AppendStage<Organizations>(new BsonDocument {
                { "$unwind", "$Priority" }
            });

            aggregation.AppendStage<Organizations>(new BsonDocument {
                { "$project", new BsonDocument { { "Name", "$Name" }, { "WorkflowCounter", new BsonDocument { { "$size", "$RelatedWorkflows" } } } } },
                { "LastDateUploaded", "$LastDateUploaded" },
                { "LastDateEvaluated", "$LastDateEvaluated"},
                { "PriorityValue", "$Priority.Value"}
            });

            aggregation.AppendStage<Organizations>(new BsonDocument {
                { "$sort", new BsonDocument { { "Priority", 1 }, { "WorkflowCounter", 1 }, { "LastDateUploaded", -1 }, { "LastDateEvaluated", -1} } }
            });

            var organizationsList = await aggregation.ToListAsync();

但是這不起作用，例如我反轉了排序選項並且總是返回相同的值。 我試圖獲得 mongo 查詢的字符串表示，但我只得到

aggregate([{ "$match" : { } }])

並且不附加聚合定義。

我嘗試使用流暢的表示法來執行查找，但我需要使用 ObjectId 和字符串字段來執行查找，因此出於這個原因，我首先在 mongodb 端解析 ObjectId 以使用第一個投影進行字符串處理，似乎沒有等價於將 ObjectId 轉換為字符串以執行查找（又名連接）的流利符號。

這是查詢在 mongo shell 上正常工作的測試證明： https : //mongoplayground.net/p/dKT8uQHjHnd

我希望從 mongo playground 示例中生成的列表中獲取第一個文檔，但我總是獲取集合的第一個元素。

Answer 1

我結束了下一步：

        var organizations = db.GetCollection<Organization>("catalog.organizations");
        var projectionOne = new BsonDocument {
                                                { "$project", new BsonDocument { 
                                                        { "_id", new BsonDocument { { "$toString", "$_id" } } },
                                                        { "Name", "$Name"},
                                                        { "LastDateUploaded", "$LastDateUploaded" },
                                                        { "LastDateEvaluated", "$LastDateEvaluated"},
                                                        { "PriorityId", "$PriorityId"}
                                                    } 
                                                }
        };

        var lookupOne = new BsonDocument {
            { "$lookup", new BsonDocument { { "from", "wfc.workflows" }, { "localField", "_id" }, { "foreignField", "Data.OrganizationId" }, { "as", "RelatedWorkflows" } } }
        };
        var lookupTwo = new BsonDocument {
            { "$lookup", new BsonDocument { { "from", "catalog.priorities" }, { "localField", "PriorityId" }, { "foreignField", "_id" }, { "as", "Priority" } } }
        };
        var unwindTwo = new BsonDocument {
            { "$unwind", "$Priority" }
        };

        var projectionTwo = new BsonDocument {
                                            { "$project", new BsonDocument { 
                                                    { "Name", "$Name" }, 
                                                    { "WorkflowCounter", new BsonDocument { { "$size", "$RelatedWorkflows" } } },
                                                    { "LastDateUploaded", "$LastDateUploaded" },
                                                    { "LastDateEvaluated", "$LastDateEvaluated"},
                                                    { "PriorityValue", "$Priority.Value"}
                                                } 
                                            }
        };

        var sort = new BsonDocument {
            { "$sort", new BsonDocument { { "PriorityValue", -1 }, { "WorkflowCounter", 1 }, { "LastDateUploaded", -1 }, { "LastDateEvaluated", -1} } }
        };

        var aggregation = organizations.Aggregate<OrganizationWithWorkflows>(new [] {projectionOne, lookupOne, lookupTwo, unwindTwo, projectionTwo, sort});

        var organizationsList = await aggregation.ToListAsync();

我創建了這個類來獲取最后的投影結果：

 [BsonIgnoreExtraElements]
 public class OrganizationWithWorkflows
 {
      public string Id { get; set; }
      public string Name { get; set; }
      public long WorkflowCounter {get; set;}
      public DateTime? LastDateUploaded { get; set; }
      public DateTime? LastDateEvaluated { get; set; }
      public int PriorityValue { get; set; }
 }

我花了一段時間，但我終於在這里解決了我的挑戰，部分是使用 ObjectId 和字符串字段執行查找，應用從 ObjectId 到字符串的強制轉換，並在同一查詢中應用多個投影和多個查找。

請注意，字段 counter 是包含在結果數組RelatedWorkflows中的元素的大小，但這也可以在 lookupOne 和分組后應用展開以使用表達式{ $sum ,1 }但在在我的情況下，使用上述數組中的 $size 表達式就足夠了。

我希望這可以幫助所有那些在理解如何使用BsonDocuments使用 MongoDB 聚合和 C# .NET 驅動程序時遇到一些麻煩的人，因為無法使用流暢的表示法創建此查詢，因為將 ObjectId 轉換為字符串並使用那個用於 lookupOne 的，也許我在最后一部分上錯了，所以如果你知道怎么做，相信我也會很高興學習它。

為了獲得我的解決方案，我從 Mikael Koskinen 找到了這篇很棒的帖子，並閱讀了 mongodb 文檔以使用表達式$toString