MongoDB - 在 C# 中映射 map-reduce 集合

发布于 2024-11-17 05:46:50 字数 934 浏览 2 评论 0原文

我正在运行一个地图缩减作业，将结果数据转储到一个集合中，“产品”集合中的元素如下所示（该结构是由 Mongo 生成的，我不知道它是否可以控制）：

{
    "_id" : { "ProductId" : "1:000001", "ProductTitle" : "Some product with ID 1:000001" }, 
    "value" : { "TotalImpressions" : 3, "TotalClicks" : 40 } 
}

理想情况下，我想要将每个条目映射到以下平面对象：

public class Product 
{
    public string ProductId { get; set; }
    public string ProductTitle { get; set; }
    public int TotalImpressions { get; set; }
}

这显然不起作用，因为序列化程序在根级别查找属性“id”和“value”，而这些属性在该类中不存在。我采取的解决方法是在对象出现时对其进行建模，例如：

public class ProductRow
{
    /* implementation of these objects excluded, but they just reflect the json objects */
    public ProductIdentifier Id { get; set; }
    public Product value { get; set; }
}

哪个映射很好，但是有点冗长，我宁愿避免拥有所有这些额外的对象。

是否可以配置 BSON 解串器来支持此映射？我浏览了文档，但没有看到任何明显的解决方案。

注意：我的工作环境仅限于 .NET 3.5，因此在考虑答案时请记住这一点。

原文

I am running a map reduce job that dumps the resulting data into a collection, the elements in the "products" collection look like this (the structure is generated by Mongo and I'm not aware if it can be controlled):

{
    "_id" : { "ProductId" : "1:000001", "ProductTitle" : "Some product with ID 1:000001" }, 
    "value" : { "TotalImpressions" : 3, "TotalClicks" : 40 } 
}

Ideally, I want to map each entry to the following flat object:

public class Product 
{
    public string ProductId { get; set; }
    public string ProductTitle { get; set; }
    public int TotalImpressions { get; set; }
}

This obviously doesn't work as the serializer looks for properties "id" and "value" at the root level, which don't exist on that class. The workaround I have in place is to model the object as they appear, e.g.:

public class ProductRow
{
    /* implementation of these objects excluded, but they just reflect the json objects */
    public ProductIdentifier Id { get; set; }
    public Product value { get; set; }
}

Which maps fine, however it's a little verbose and I'd rather avoid having all those extra objects.

Is it possible to configure the BSON deserializer to support this mapping? I've had a look through the documentation, but haven't seen any obvious solution.

NB: I am restricted by working environment to .NET 3.5, so please bear that in mind when considering an answer.

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吻风 2024-11-24 05:46:50

您可以轻松地自己进行反序列化（如@Avish建议的那样），所以这里是您的案例的完整示例：

var mongoServer = MongoServer.Create("mongodb://localhost:27020");
var database = mongoServer.GetDatabase("StackoverflowExamples");
var products = database.GetCollection("products");

var result = new Product();

var item = products.FindOne();
var id = item["_id"].ToBsonDocument();
var value = item["value"].ToBsonDocument();

result.ProductId = id["ProductId"].AsString;
result.ProductTitle = id["ProductTitle"].AsString;
result.TotalImpressions = value["TotalImpressions"].AsInt32;

You can easy do deserialization yourself(as @Avish suggested), so here is complete example for your case:

var mongoServer = MongoServer.Create("mongodb://localhost:27020");
var database = mongoServer.GetDatabase("StackoverflowExamples");
var products = database.GetCollection("products");

var result = new Product();

var item = products.FindOne();
var id = item["_id"].ToBsonDocument();
var value = item["value"].ToBsonDocument();

result.ProductId = id["ProductId"].AsString;
result.ProductTitle = id["ProductTitle"].AsString;
result.TotalImpressions = value["TotalImpressions"].AsInt32;

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