MongoDB.Driver是操作mongo数据库的驱动，最近2.0以下版本已经从GitHub和Nuget中移除了，也就是说.NET Framework4.0不再能从官方获取到MongoDB的驱动了，其次MongoDB.Driver2.0开始API变更巨大，本文不适用MongoDB.Driver2.0以下版本，亦不适用.NET Framework4.5以下版本

要在.NET中使用MongoDB，就必须引用MongoDB的驱动，使用Nuget安装MongoDB.Driver是最方便的，目前Nuget支持的MongoDB程序包有对.NET Framework4.5以上版本的依赖

安装完成之后会在引用中新增三个MongoDB的程序集引用，其中MongoDB.Driver.Core在2.0版本以下是没有的

先构建一个实体基类，因为Mongo要求每个文档都有唯一Id,默认为ObjectId类型（根据时间Mac地址Pid算出来的，类似GUID，适用于分布式），在这个基类中添加Id属性

using MongoDB.Bson;using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace MongoTest{    /// 
    /// 自定义类型Id    /// 
    /// 
          public abstract class BaseEntity
      
           {        public T Id { get; set; }    }    /// 
       
    /// Mongo默认填充ObjectId类型的Id    /// 
    public abstract class DefaultIdEntity : BaseEntity
       
            {    }}
       
      

开始构建数据库访问类DbContext

using MongoDB.Driver;using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace MongoTest{    public class DbContext    {        public readonly IMongoDatabase _db;        public DbContext()        {            //此为开启验证模式 必需使用用户名 密码 及指定登陆的数据库 可采用,分割连接多个数据库            var client = new MongoClient("mongodb://root:123456@192.168.20.54:27017/admin");            //未开启验证模式数据库连接            // var client = new MongoClient("mongodb://127.0.0.1:27017");             //指定要操作的数据库            _db = client.GetDatabase("mytest");        }        private static string InferCollectionNameFrom
      
       ()        {            var type = typeof(T);            return type.Name;        }        public IMongoCollection
       
         Collection
        
         () where T : BaseEntity
         
                  {            var collectionName = InferCollectionNameFrom
          
           ();            return _db.GetCollection
           
            (collectionName); } /// 
            
 /// 实体类名和数据库中文档（关系型数据库中的表）名一致时使用 /// 
 public IMongoCollection
            
              Collection
             
              () where T : DefaultIdEntity { var collectionName = InferCollectionNameFrom
              
               (); return _db.GetCollection
               
                (collectionName); } public IMongoCollection
                
                  Collection
                 
                  (string collectionName) where T : BaseEntity
                  
                    { return _db.GetCollection
                   
                    (collectionName); } /// 
                    
 /// 实体类名和数据库中文档（关系型数据库中的表）不一致时使用，通过collectionName指定要操作得文档 /// 
 public IMongoCollection
                    
                      Collection
                     
                      (string collectionName) where T : DefaultIdEntity { return _db.GetCollection
                      
                       (collectionName); } }}
                      
                     
                    
                   
                  
                 
                
               
              
             
            
           
          
         
        
       
      

现有数据库数据 文档book 包含数据如下

开始构建与文档对应的实体，mongo是文档数据库，对单词得大小写是敏感得，所以构建的实体的字段也应该是小写的，有点不符合习惯

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace MongoTest{    public class book : DefaultIdEntity    {        public string title { get; set; }        public double price { get; set; }        public string author { get; set; }        public string publisher { get; set; }        public int saleCount { get; set; }    }}

现在开始增删查改操作，其中查找和删除的filter参数有两种形式，lambda和Definition

using MongoDB.Driver;using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace MongoTest{    public class OperatDb    {        static IMongoCollection
      
        bookDao;        static OperatDb()        {            bookDao = new DbContext().Collection
       
        ();        }        public static void Excute()        {            Console.WriteLine();            QueryAll();            Console.WriteLine();            Query();            Console.WriteLine();            Insert();            Console.WriteLine();            QueryAll();            Console.WriteLine();            Update();            Console.WriteLine();            Delete();            Console.WriteLine();            QueryAll();            Console.ReadKey();        }        public static void QueryAll()        {            var books = bookDao.Find(x => true).ToList();            foreach (var item in books)            {                Console.WriteLine(item.ToString());            }        }        public static void Query(System.Linq.Expressions.Expression
        
         
          > filter = null)        {            if (filter == null) filter = x => x.author == "韩寒";            var books = bookDao.Find(filter).ToList();            foreach (var item in books)            {                Console.WriteLine(item.ToString());            }        }        public static void Update()        {            var filter = Builders
          
           .Filter.Eq(x => x.title, "悲伤逆流成河");            var book = bookDao.Find(filter).FirstOrDefault();            Console.WriteLine("更新前：{0}", book.ToString());            var update = Builders
           
            .Update.Set(x => x.publisher, "新时代出版社") .Set(x => x.price, 35) .Inc(x => x.saleCount, 10); var result = bookDao.UpdateOne(filter, update); Console.WriteLine("IsAcknowledged:{0} MatchedCount:{1} UpsertedId:{2} IsModifiedCountAvailable:{3} ModifiedCount:{4}", result.IsAcknowledged, result.MatchedCount, result.UpsertedId, result.IsModifiedCountAvailable, result.ModifiedCount); book = bookDao.Find(filter).FirstOrDefault(); Console.WriteLine("更新后：{0}", book.ToString()); } public static void Delete() { var result = bookDao.DeleteOne(x => x.title == "悲伤逆流成河"); Console.WriteLine("DeletedCount:{0} IsAcknowledged:{1} ", result.DeletedCount, result.IsAcknowledged); } public static void Insert() { var bookInfo = new book { Id = new MongoDB.Bson.ObjectId(), author = "郭敬明", price = 10.00, publisher = "春风文艺出版社", saleCount = 0, title = "悲伤逆流成河" }; bookDao.InsertOne(bookInfo); } }}
           
          
         
        
       
      

 因为我对book类的ToString方法进行了重写，所以输出结果如下

上面都是用的数据库和实体字段名一致的情况，如果不一致怎么办呢，Xml和Json等序列化都有标签特性可以用别名，Bson肯定也会有，新建BookInfo实体如下

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace MongoTest{    public class BookInfo : DefaultIdEntity    {        public string Title { get; set; }        public double Price { get; set; }        public string Author { get; set; }        public string Publisher { get; set; }        public int SaleCount { get; set; }    }}

将上面执行操作的book全部替换成BookInfo试试，发现没报错，再去数据库看看会发现，数据库新增了一个文档，我们预期得结果是要操作在book上，显然这不是我们想要的

现在将调用Collection调用改为指定collectionName为book的形式

static IMongoCollection
     
       bookDao;        static OperatDb()        {            bookDao = new DbContext().Collection
      
       ("book");        }
      
     

再次运行程序，发现报错了，文档节点和实体字段不匹配

现在给BookInfo的字段都加上Bson的标签特性

using MongoDB.Bson.Serialization.Attributes;using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace MongoTest{    public class BookInfo : DefaultIdEntity    {        [BsonElement("title")]        public string Title { get; set; }        [BsonElement("price")]        public double Price { get; set; }        [BsonElement("author")]        public string Author { get; set; }        [BsonElement("publisher")]        public string Publisher { get; set; }        [BsonElement("saleCount")]        public int SaleCount { get; set; }    }}

现在一切正常了，显示结果和之前的一样就不再贴图了，有子文档的数据操作与此类似，譬如有如下数据

构建实体如下

public class Director : Entity    {        [BsonElement("name")]        public string Name { get; set; }        [BsonElement("country")]        public string Country { get; set; }        [BsonElement("age")]        public int Age { get; set; }        [BsonElement("movies")]        public List
      
        Movies { get; set; }    }    public class Movie    {        [BsonElement("name")]        public string Name { get; set; }        [BsonElement("year")]        public int Year { get; set; }    }