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Fundamentals

LINQ

在此页面上

  • Overview
  • 将集合设为可查询
  • 支持的聚合阶段
  • $project
  • $match
  • $limit
  • $skip
  • $unwind
  • $group
  • $sort
  • $lookup
  • $vectorSearch
  • 按位操作符
  • $bitAnd
  • $bitOr
  • $bitNot
  • $bitXor
  • 不支持的聚合阶段
  • 支持的方法
  • 查看已翻译的查询

Overview

在本指南中，您可以学习；了解如何将 LINQ 与MongoDB .NET/ C#驱动程序结合使用。LINQ 允许使用语言关键字和操作符来构造针对强类型对象集合的查询。 .NET/ C#驱动程序自动将 LINQ 查询转换为聚合操作。

重要

LINQ3 是 MongoDB .NET/C# 驱动程序中唯一可用的 LINQ 提供商。如果您已手动将项目配置为使用 LINQ2，则其无法编译。

本指南中的示例使用 Atlas 样本数据集所提供的 sample_restaurants 数据库中的 restaurants 集合。要了解如何创建免费的 MongoDB Atlas 集群并加载示例数据集，请参阅快速入门。

以下 Restaurant、Address 和 GradeEntry 类将为该集合中的文档建模：

public class Restaurant
{
    public ObjectId Id { get; set; }
    public string Name { get; set; }
    [BsonElement("restaurant_id")]
    public string RestaurantId { get; set; }
    public string Cuisine { get; set; }
    public Address Address { get; set; }
    public string Borough { get; set; }
    public List<GradeEntry> Grades { get; set; }
}
public class Address
{
    public string Building { get; set; }
    [BsonElement("coord")]
    public double[] Coordinates { get; set; }
    public string Street { get; set; }
    [BsonElement("zipcode")]
    public string ZipCode { get; set; }
}
public class GradeEntry
{
    public DateTime Date { get; set; }
    public string Grade { get; set; }
    public float Score { get; set; }
}

注意

restaurants集合中的文档使用蛇形命名规则。本指南中的示例使用 ConventionPack 将集合中的字段反序列化为 Pascal 语句，并将它们映射到 Restaurant 类中的属性。

如需了解有关自定义序列化的更多信息，请参阅“自定义序列化”。

将集合设为可查询

要使用 LINQ 查询您的集合，必须先创建一个链接到该集合的 iQueryable 对象。要创建对象，请使用 AsQueryable() 方法，如下所示：

var restaurantsDatabase = client.GetDatabase("sample_restaurants");
var restaurantsCollection = restaurantsDatabase.GetCollection<Restaurant>("restaurants");
var queryableCollection = restaurantsCollection.AsQueryable();

获得可查询对象后，您可以使用方法语法组成查询。一些管道阶段还支持查询理解语法，类似于 SQL 查询语法。

选择 Method Syntax（方法语法）或 Query Syntax（查询语法）标签页，查看如何使用 LINQ 创建查询：

var query = queryableCollection
    .Where(r => r.Name == "The Movable Feast")
    .Select(r => new { r.Name, r.Address });
var query = from r in queryableCollection
    where r.Name == "The Movable Feast"
    select new { r.Name, r.Address };

您可以按如下方式输出上述示例的结果：

foreach (var restaurant in query)
{
    Console.WriteLine(restaurant.ToJson());
}
{ "name" : "The Movable Feast", "address" : { "building" : "284", "coord" : [-73.982923900000003, 40.6580753], "street" : "Prospect Park West", "zipcode" : "11215" } }

提示

访问查询结果

您还可以使用 ToList() 或 ToCursor() 方法访问查询结果：

var results = query.ToList();
var results = query.ToCursor();

支持的聚合阶段

您可以使用 LINQ 来创建聚合管道。.NET/C# 驱动程序会自动将每个 LINQ 语句转换为相应的聚合管道阶段。在本节中，您可以了解哪些聚合管道阶段受到支持。

要了解有关聚合管道阶段的更多信息，请参阅服务器手册中的聚合阶段页面。

$project

$project 聚合阶段返回仅包含指定字段的文档。

选择 Method Syntax（方法语法）或 Query Syntax （查询语法）标签页以查看如何使用 LINQ 生成 $project 阶段：

var query = queryableCollection
    .Select(r => new { r.Name, r.Address });
var query = from r in queryableCollection
    select new { r.Name, r.Address };

上述示例的结果包含以下文档：

{ "name" : "The Movable Feast", "address" : { "building" : "284", "coord" : [-73.982923900000003, 40.6580753], "street" : "Prospect Park West", "zipcode" : "11215" } }

注意

排除 _id 字段

如果您不在 LINQ 投影中包含 _id 字段，.NET/C# 驱动程序会自动将其从结果中排除。

$match

$match 聚合阶段将返回与指定条件匹配的文档。

选择 Method Syntax（方法语法）或 Query Syntax （查询语法）标签页以查看如何使用 LINQ 生成 $match 阶段：

var query = queryableCollection
    .Where(r => r.Name == "The Movable Feast");
var query = from r in queryableCollection
    where r.Name == "The Movable Feast"
    select r;

上述示例的结果包含以下文档：

// Results Truncated
{ "_id" : ObjectId(...), "name" : "The Movable Feast", "restaurant_id" : "40361606", "cuisine" : "American", "address" : {...}, "borough" : "Brooklyn", "grades" : [...] }

$limit

$limit 聚合阶段限制查询返回的文档数量。下面的示例展示了如何使用 LINQ 生成 $limit 阶段：

var query = queryableCollection
    .Where(r => r.Cuisine == "Italian")
    .Select(r => new {r.Name, r.Cuisine})
    .Take(5);

上述示例的结果包含以下文档：

{ "name" : "Philadelhia Grille Express", "cuisine" : "Italian" }
{ "name" : "Isle Of Capri Resturant", "cuisine" : "Italian" }
{ "name" : "Marchis Restaurant", "cuisine" : "Italian" }
{ "name" : "Crystal Room", "cuisine" : "Italian" }
{ "name" : "Forlinis Restaurant", "cuisine" : "Italian" }

$skip

$skip 聚合阶段会跳过查询返回的指定数量的文档，并返回其余结果。下面的示例展示了如何使用 LINQ 生成 $skip 阶段：

var query = queryableCollection
    .Where(r => r.Cuisine == "Italian")
    .Select(r => new {r.Name, r.Cuisine})
    .Skip(2);

前面的示例跳过了符合条件的前两家餐厅，并返回其余的餐厅。结果包含以下文档：

// Results Truncated
{ "name" : "Marchis Restaurant", "cuisine" : "Italian" }
{ "name" : "Crystal Room", "cuisine" : "Italian" }
{ "name" : "Forlinis Restaurant", "cuisine" : "Italian" }
...

$unwind

$unwind 聚合阶段解构指定的数组字段，并为该数组中的每个元素返回一个文档。

选择 Method Syntax（方法语法）或 Query Syntax（查询语法）标签页以查看如何使用 LINQ 生成 $unwind 阶段：

var query = queryableCollection
    .Where(r => r.Name == "The Movable Feast")
    .SelectMany(r => r.Grades);
var query = from r in queryableCollection
    where r.Name == "The Movable Feast"
    from grade in r.Grades
    select grade;

上述示例中的查询会查找 Name 字段具有“The Movable Feast”值的文档。然后，对于此文档的 Grades 数组中的每个元素，该查询均会返回一个新文档。结果包含以下文档：

{ "date" : ISODate("2014-11-19T00:00:00Z"), "grade" : "A", "score" : 11 }
{ "date" : ISODate("2013-11-14T00:00:00Z"), "grade" : "A", "score" : 2 }
{ "date" : ISODate("2012-12-05T00:00:00Z"), "grade" : "A", "score" : 13 }
{ "date" : ISODate("2012-05-17T00:00:00Z"), "grade" : "A", "score" : 11 }

$group

$group 聚合阶段会根据您指定的条件将文档分为多个群组。

选择 Method Syntax（方法语法）或 Query Syntax（查询语法）标签页以查看如何使用 LINQ 生成 $group 阶段：

var query = queryableCollection
    .GroupBy(r => r.Cuisine)
    .Select(g => new { Cuisine = g.Key, Count = g.Count() });
var query = from r in queryableCollection
    group r by r.Cuisine into g
    select new {Cuisine = g.Key, Count = g.Count()};

前面的示例按每个文档的Cuisine字段中的值对各文档进行分组，然后计算具有每个Cuisine值的文档数量。结果包含以下文件：

// Results Truncated
{ "cuisine" : "Caribbean", "count" : 657 }
{ "cuisine" : "Café/Coffee/Tea", "count" : 1214 }
{ "cuisine" : "Iranian", "count" : 2 }
{ "cuisine" : "Nuts/Confectionary", "count" : 6 }
{ "cuisine" : "Middle Eastern", "count" : 168 }
...

注意

结果顺序

上述查询并非总以同一顺序返回结果。运行此示例所返回结果的顺序可能与上述顺序不同。

$sort

$sort聚合阶段按您指定的顺序返回查询结果。

选择 Method Syntax（方法语法）或 Query Syntax（查询语法）标签页以查看如何使用 LINQ 生成 $sort 阶段：

var query = queryableCollection
    .OrderBy(r => r.Name)
    .ThenByDescending(r => r.RestaurantId);
var query = from r in queryableCollection
    orderby r.Name, r.RestaurantId descending
    select r;

上例按 Name 字段的字母顺序返回查询结果，并对 RestaurantId 字段进行二级降序排序。以下是返回结果中包含的文档的子集：

// Results Truncated
...
{ "_id" : ObjectId(...), "name" : "Aba Turkish Restaurant", "restaurant_id" : "41548686", "cuisine" : "Turkish", "address" : {...}, "borough" : "Manhattan", "grades" : [...] }
{ "_id" : ObjectId(...), "name" : "Abace Sushi", "restaurant_id" : "50006214", "cuisine" : "Japanese", "address" : { ... }, "borough" : "Manhattan", "grades" : [...] }
{ "_id" : ObjectId(...), "name" : "Abacky Potluck", "restaurant_id" : "50011222", "cuisine" : "Asian", "address" : { ... }, "borough" : "Manhattan", "grades" : [...] }
{ "_id" : ObjectId(...), "name" : "Abaleh", "restaurant_id" : "50009096", "cuisine" : "Mediterranean", "address" : { ... }, "borough" : "Manhattan", "grades" : [...] }
...

$lookup

$lookup 聚合阶段将同一数据库中一个集合中的文档与另一集合中的文档连接起来。$lookup 阶段向每个输入文档添加一个新的数量字段。新的大量字段包含来自“已加入”收集的匹配文档。

注意

要执行查找，必须使用 AsQueryable() 方法使两个集合都可进行查询。

要了解如何让集合可供查询，请参阅让集合可供查询。

以 sample_restaurants 数据库中名为 reviews 的第二个集合（其中包含餐厅评价）为例。您可以使用 $lookup 阶段将该集合中的文档联接到 restaurants 集合中具有相同 name 值的文档。

以下 Review 类对 reviews 集合中的文档进行建模：

public class Review
{
    public ObjectId Id { get; set; }
    [BsonElement("restaurant_name")]
    public string RestaurantName { get; set; }
    public string Reviewer { get; set; }
    [BsonElement("review_text")]
    public string ReviewText { get; set; }
}

选择 Method Syntax（方法语法）或 Query Syntax（查询语法）标签页以查看如何使用 LINQ 生成 $lookup 阶段：

var query = queryableCollection
    .GroupJoin(reviewCollection,
        restaurant => restaurant.Name,
        review => review.RestaurantName,
        (restaurant, reviews) =>
            new { Restaurant = restaurant, Reviews = reviews }
    );
var query = from restaurant in queryableCollection
    join rv in reviewCollection on restaurant.Name equals rv.RestaurantName into reviews
    select new { restaurant, reviews };

上述示例返回来自 restaurants 集合的所有文档。每个餐厅文档都添加了一个名为 reviews 的字段，其中包含该餐厅的所有评论。如果评论文档中的 name 字段的值与餐厅文档的 name 字段匹配，则评论与餐厅匹配。

以下显示的是返回结果的一个子集：

// Results Truncated
{
   "restaurant": {
      "_id": ObjectId("..."),
      "name": "The Movable Feast",
      "restaurant_id": "40361606",
      "cuisine": "American",
      "address": { ... },
      "borough": "Brooklyn",
      "grades": [ ... ]
   },
   "reviews": [
      {
         "_id": ObjectId("..."),
         "restaurant_name": "The Movable Feast",
         "reviewer": "Lazlo Cravensworth",
         "review_text": "Great restaurant! 12/10 stars!"
      },
      {
         "_id": ObjectId("..."),
         "restaurant_name": "The Movable Feast",
         "reviewer": "Michael Scarn",
         "review_text": "It really was a feast"
      }
   ]
}

$vectorSearch

$vectorSearch 聚合阶段对指定字段中的矢量执行近似最近邻搜索。在对数据进行向量搜索之前，您的数据集必须有一个已定义的 Atlas Vector Search 索引。

提示

要获取以下示例中使用的示例数据集，请参阅快速入门。要创建以下示例中使用的示例 Atlas Vector Search 索引，请参阅 Atlas 手册中的创建 Atlas Vector Search 索引。

考虑 sample_mflix 数据库中的 embedded_movies 集合。您可以使用 $vectorSearch 阶段对集合中文档的 plot_embedding 字段执行语义搜索。

以下 EmbeddedMovie 类对 embedded_movies 集合中的文档进行建模：

[BsonIgnoreExtraElements]
public class EmbeddedMovie
{
   [BsonIgnoreIfDefault]
   public string Title { get; set; }
   public string Plot { get; set; }
   [BsonElement("plot_embedding")]
   public double[] Embedding { get; set; }
}

以下示例展示了如何生成 $vectorSearch 阶段，以便使用向量嵌入在 plot_embedding 字段中搜索字符串 "time travel" ：

// Defines vector embeddings for the string "time travel"
var vector = new[] 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// Specifies that the vector search will consider the 150 nearest neighbors
// in the specified index
var options = new VectorSearchOptions<EmbeddedMovie>()
{
   IndexName = "vector_index",
   NumberOfCandidates = 150
};
// Builds aggregation pipeline and specifies that the $vectorSearch stage
// returns 10 results
var results = queryableCollection
   .VectorSearch(m => m.Embedding, vector, 10, options)
   .Select(m => new { m.Title, m.Plot });

上述示例的结果包含以下文档：

{ "_id" : ObjectId("573a13a0f29313caabd04a4f"), "plot" : "A reporter, learning of time travelers visiting 20th century disasters, tries to change the history they know by averting upcoming disasters.", "title" : "Thrill Seekers" }
{ "_id" : ObjectId("573a13d8f29313caabda6557"), "plot" : "At the age of 21, Tim discovers he can travel in time and change what happens and has happened in his own life. His decision to make his world a better place by getting a girlfriend turns out not to be as easy as you might think.", "title" : "About Time" }
{ "_id" : ObjectId("573a13a5f29313caabd13b4b"), "plot" : "Hoping to alter the events of the past, a 19th century inventor instead travels 800,000 years into the future, where he finds humankind divided into two warring races.", "title" : "The Time Machine" }
{ "_id" : ObjectId("573a13aef29313caabd2e2d7"), "plot" : "After using his mother's newly built time machine, Dolf gets stuck involuntary in the year 1212. He ends up in a children's crusade where he confronts his new friends with modern techniques...", "title" : "Crusade in Jeans" }
{ "_id" : ObjectId("573a1399f29313caabceec0e"), "plot" : "An officer for a security agency that regulates time travel, must fend for his life against a shady politician who has a tie to his past.", "title" : "Timecop" }
{ "_id" : ObjectId("573a1399f29313caabcee36f"), "plot" : "A time-travel experiment in which a robot probe is sent from the year 2073 to the year 1973 goes terribly wrong thrusting one of the project scientists, a man named Nicholas Sinclair into a...", "title" : "A.P.E.X." }
{ "_id" : ObjectId("573a13c6f29313caabd715d3"), "plot" : "Agent J travels in time to M.I.B.'s early days in 1969 to stop an alien from assassinating his friend Agent K and changing history.", "title" : "Men in Black 3" }
{ "_id" : ObjectId("573a13d4f29313caabd98c13"), "plot" : "Bound by a shared destiny, a teen bursting with scientific curiosity and a former boy-genius inventor embark on a mission to unearth the secrets of a place somewhere in time and space that exists in their collective memory.", "title" : "Tomorrowland" }
{ "_id" : ObjectId("573a13b6f29313caabd477fa"), "plot" : "With the help of his uncle, a man travels to the future to try and bring his girlfriend back to life.", "title" : "Love Story 2050" }
{ "_id" : ObjectId("573a13e5f29313caabdc40c9"), "plot" : "A dimension-traveling wizard gets stuck in the 21st century because cell-phone radiation interferes with his magic. With his home world on the brink of war, he seeks help from a jaded ...", "title" : "The Portal" }

有关 Atlas Vector Search、Atlas Vector Search 索引以及如何将其纳入应用程序的更多信息，请参阅 Atlas 手册中的Atlas Vector Search 概述。有关使用 .NET/C# 驱动程序运行 Atlas Vector Search 查询的更多示例，请参阅 Atlas 手册中的运行向量搜索查询，并从语言下拉菜单中选择 C#。

按位操作符

本节介绍可在聚合管道中使用的.NET/ C#驱动程序支持的按位运算符。您可以在同一阶段使用多个按位运算符。 使用按位运算符时，应用以下准则：

  • 所有操作数的类型必须为 int 或 long。

  • $bitAnd、$bitOr 和 $bitXor 接受两个或多个操作数。$bitNot 需要一个操作数。

  • 按位运算的计算顺序是从左到右。

本部分中的示例使用名为 ingredients 的集合中的以下文档：

{ "_id" : 1, "name" : "watermelon", "is_available" : 1, "is_cheap" : 1 },
{ "_id" : 2, "name" : "onions", "is_available" : 1, "is_cheap" : 0 },
{ "_id" : 3, "name" : "eggs", "is_available" : 0, "is_cheap" : 0 },
{ "_id" : 4, "name" : "potatoes", "is_available" : 1, "is_cheap" : 1 },
{ "_id" : 5, "name" : "pasta", "is_available" : 0, "is_cheap" : 1 },
{ "_id" : 6, "name" : "cheese", "is_available" : 1 }

"is_available"字段表示某种成分是否可用。如果此字段的值为 0，则表明该成分不可用。如果其值为 1，则该成分可用。

"is_cheap"字段表示某种成分是否便宜。如果此字段的值为 0 ，则该成分并不便宜。如果其值为 1 ，则该成分很便宜。

以下 Ingredient 类对 ingredients 集合中的文档进行建模：

public class Ingredient 
{
    public int Id { get; set; }
    public string Name { get; set; }
    [BsonElement("is_available")]
    public int? IsAvailable { get; set; }
    [BsonElement("is_cheap")]
    public int? IsCheap { get; set; }
}

注意

缺失或未定义的操作数

如果传递给任何按位运算操作符的操作数的类型为可空 int或long ，且包含缺失或未定义的值，则整个表达式的计算结果为null 。如果操作数的类型不可为空 int 或 long 且包含缺失或未定义的值，则.NET/ C#驱动程序将引发错误。

$bitAnd

$bitAnd聚合操作符对给定参数执行按位 AND 运算。您可以通过使用 & 字符连接两个或多个子句来使用 $bitAnd操作符符。

以下示例演示如何使用 LINQ 创建 $bitAnd 阶段。该代码检索 Name字段值为 "watermelon" 的文档。然后，它对此文档中 IsAvailable 和 IsCheap 字段的值执行按位 AND 运算。

var query = queryableCollection
    .Where(i => i.Name == "watermelon")
    .Select(i => i.IsAvailable & i.IsCheap);

前面的代码返回 1，即对 IsAvailable字段(1) 和 IsCheap字段(1) 的值执行 AND 操作的结果。

以下示例对集合中的所有文档执行相同的按位 AND 操作：

var query = queryableCollection
    .Select(i => i.IsAvailable & i.IsCheap);
1
0
0
1
0
null

null 结果来自 Name字段值为 "cheese" 的文档。此文档缺少 IsCheap字段，因此表达式的计算结果为 null。

$bitOr

$bitOr聚合操作符对给定参数执行按位 OR 运算。您可以通过使用 | 字符连接两个或多个子句来使用 $bitOr操作符符。

以下示例演示如何使用 LINQ 创建 $bitOr 阶段。该代码检索 Name字段值为 "onions" 的文档。然后，它对此文档中 IsAvailable 和 IsCheap 字段的值执行按位 OR 运算。

var query = queryableCollection
    .Where(i => i.Name == "onions")
    .Select(i => i.IsAvailable | i.IsCheap);

前面的代码返回 1，即对 IsAvailable字段(1) 和 IsCheap字段(0) 的值进行 OR 运算的结果。

$bitNot

$bitNot聚合操作符对给定参数执行按位 NOT 运算。您可以通过在操作数前添加 ~ 字符来使用 $bitNot操作符符。$bitNot 仅接受一个参数。以下示例展示了如何使用 LINQ 创建 $bitNot 阶段：

var query = queryableCollection
    .Select(i => ~i.IsCheap);
-2
-1
-1
-2
-2
null

$bitXor

$bitXor聚合操作符对给定参数执行按位 XOR 运算。您可以通过使用 ^ 字符连接两个或多个子句来使用 $bitXor操作符符。

以下示例演示如何使用 LINQ 创建 $bitXor 阶段。该代码检索 Name字段值为 "watermelon" 或 "onions" 的文档。然后，它对这些文档中 IsAvailable 和 IsCheap 字段的值执行按位 XOR 运算。

var query = queryableCollection
    .Where(i => i.Name == "watermelon" || i.Name == "onions")
    .Select(i => i.IsAvailable ^ i.IsCheap);

结果包含以下值：

0
1

不支持的聚合阶段

LINQ 的 MongoDB .NET/C# Driver 实现不支持以下聚合阶段：

  • $redact

  • $geoNear

  • $out

要了解如何使用构建器创建具有 $out 阶段的聚合管道，请参阅将管道结果写入集合部分。

支持的方法

以下是 LINQ 的MongoDB .NET/ C#驱动程序实施支持的一些方法：

方法名称
说明

Any

确定是否有文档符合指定条件

Average

计算指定字段的平均值

Count

返回 Int32，表示符合指定条件的文档数量

LongCount

返回 Int64，表示符合指定条件的文档数量

DateFromString

将 string 转换为 DateTime对象

Distinct

返回符合指定条件的不同文档

Exists

测试字段是否存在

First

返回第一个匹配的文档，如果未找到，则引发异常

FirstOrDefault

返回第一个匹配的文档，如果未找到，则返回 null

GroupBy

根据指定标准对文档分组

GroupJoin

对同一数据库中的另一个集合执行左外连接

IsMissing

如果字段缺失，则返回 true，否则返回 false

IsNullOrMissing

如果字段为 null 或缺失，则返回 true，否则返回 false

Max

返回具有最大指定值的文档

OfType

返回与指定类型匹配的文档

OrderBy, OrderByDescending

按指定的排序顺序返回结果

ThenBy, ThenByDescending

允许指定辅助排序

Select

根据指定的条件选择文档

SelectMany

投影序列中的每个元素，并将生成的序列合并到一个文档中

Single

返回唯一匹配的文档，如果没有完全匹配的文档，则抛出异常

SingleOrDefault

返回匹配的文档，如果没有匹配的文档，则返回 null

Skip

跳过指定数量的文档，并返回其余结果

Sum

返回指定字段中值的总和

Take

指定要返回的结果数

Where

返回符合指定条件的所有文档

查看已翻译的查询

运行 LINQ 查询时，.NET/C# 驱动程序会自动将查询转换为使用 MongoDB Query API 编写的聚合管道。您可以使用 ToString() 方法或 LoggedStages 属性查看已翻译的查询。

若要查看非标量操作的已转换查询，请使用 ToString() 方法。非标量操作是指返回查询对象的操作，例如：

  • Where

  • Select

  • SelectMany

  • GroupJoin

下面的示例对 LINQ 查询调用 ToString() 方法并打印已翻译的查询：

 var queryableCollection = _restaurantsCollection.AsQueryable();
 var query = queryableCollection
      .Where(r => r.Name == "The Movable Feast");
 var queryTranslated = query.ToString();
 Console.WriteLine(queryTranslated);
sample_restaurants.restaurants.Aggregate([{ "$match" : { "name" : "The Movable Feast" } }])

要获取标量操作的已翻译查询，请使用 LoggedStages 属性。标量操作是返回标量结果而不是查询对象的操作，例如：

  • First

  • Sum

  • Count

  • Min

  • Max

要获取带有 LoggedStages 属性的已翻译查询，必须在执行已翻译的查询之后，以及使用相同可查询对象执行任何其他查询之前直接保存该查询。

下面的示例对使用标量操作的 LINQ 查询使用 LoggedStages 属性，然后打印已翻译的查询：

var queryableCollection = _restaurantsCollection.AsQueryable();
var query = queryableCollection
    .Where(r => r.Name == "The Movable Feast");
var result = query.FirstOrDefault();
var queryTranslated = query.LoggedStages;
Console.WriteLine(queryTranslated.ToJson());
[{ "$match" : { "name" : "The Movable Feast" } }, { "$limit" : NumberLong(1) }]

重要

LoggedStages 不是线程安全的。执行查询并从多个线程访问关联的 LoggedStages 属性可能会产生不确定的结果。

后退

聚合(Aggregation)

来年

BSON 操作