//扩展方法public static class ServiceCollectionExtensions
 {
 public static void AddMongoDB(this IServiceCollection services, IConfiguration configuration)
 {
  services.Configure<Settings>(options =>
  {
  options.ConnectionString = configuration.GetSection("MongoConnection:ConnectionString").Value;
  options.Database = configuration.GetSection("MongoConnection:Database").Value;
  });
 }
 }

public class MongoDBBase
 {
 private readonly IMongoDatabase _database = null;
 public MongoDBBase(string connectionString, string databaseName)
 {
  var client = new MongoClient(connectionString);
  if (client != null)
  {
  _database = client.GetDatabase(databaseName);
  }
 }

 #region SELECT
 /// <summary>
 /// 根据查询条件，获取数据
 /// </summary>
 /// <typeparam name="T"></typeparam>
 /// <param name="id"></param>
 /// <returns></returns>
 public List<T> GetList<T>(Expression<Func<T, bool conditions = null)
 {
  var collection = _database.GetCollection<T>(typeof(T).Name);
  if (conditions != null)
  {
  return collection.Find(conditions).ToList();
  }
  return collection.Find(_ => true).ToList();
 }#endregion

 #region INSERT/// <summary>
 /// 插入多条数据，数据用list表示
 /// </summary>
 /// <typeparam name="T"></typeparam>
 /// <param name="list"></param>
 /// <returns></returns>
 public List<T> InsertMany<T>(List<T> list)
 {
  var collection = _database.GetCollection<T>(typeof(T).Name);
  collection.InsertMany(list);
  return list;
 }
 #endregion
 }

 "MongoConnection": { //mongodb数据库连接
 "ConnectionString": "mongodb://127.0.0.1:27017",
 "Database": "testdb",
 "IsSSL": true
 },

[Produces("application/json")]
 [Route("api/MongoDB/[action]")]
 public class MongoDBController : Controller
 {
  private readonly MongoDBBase _context = null;
  public MongoDBController(IOptions<Settings> settings)
  {
   _context = new MongoDBBase(settings.Value.ConnectionString, settings.Value.Database);
  }
  [HttpGet]
  public IActionResult AddList()
  {
   List<MongoDBPostTest> list = new List<MongoDBPostTest>()
   {
    new MongoDBPostTest()
    {
     Id = "2",
     Body = "Test note 3",
     UpdatedOn = DateTime.Now,
     UserId = 1,
     HeaderImage = new NoteImage
     {
      ImageSize = 10,
      Url = "http://localhost/image1.png",
      ThumbnailUrl = "http://localhost/image1_small.png"
     }
    },
    new MongoDBPostTest()
    {
     Id = "3",
     Body = "Test note 4",
     UpdatedOn = DateTime.Now,
     UserId = 1,
     HeaderImage = new NoteImage
     {
      ImageSize = 14,
      Url = "http://localhost/image3.png",
      ThumbnailUrl = "http://localhost/image3_small.png"
     }
    }
   };

   try
   {
    _context.InsertMany(list);
   }
   catch (Exception ex)
   {

    throw;
   }

   return Ok("成功");
  }

  [HttpGet]
  public Result<List<MongoDBPostTest SelectSingle()
  {
   //无条件
   var list = _context.GetList<MongoDBPostTest>();

   //有条件
   //var list = _context.GetList<MongoDBPostTest>(a => a.Id == "1");

   //得到单条数据,无条件
   //var list = _context.GetSingle<MongoDBPostTest>();

   //得到单条数据,有条件
   //var list = _context.GetSingle<MongoDBPostTest>(a => a.Id == "3");

   ObjectId internalId = _context.GetInternalId("5bbf41651d3b66668cbb5bfc");

   var a = _context.GetSingle<MongoDBPostTest>(note => note.Id == "5bbf41651d3b66668cbb5bfc" || note.InternalId == internalId);

   return ResHelper.Suc(1, list, "成功");
  }
}

public class MongoDBPostTest
 {
  [BsonId]
  // standard BSonId generated by MongoDb
  public ObjectId InternalId { get; set; }
  public string Id { get; set; }

  public string Body { get; set; } = string.Empty;

  [BsonDateTimeOptions]
  public DateTime UpdatedOn { get; set; } = DateTime.Now;

  public NoteImage HeaderImage { get; set; }

  public int UserId { get; set; } = 0;
 }

public class NoteImage
 {
  public string Url { get; set; } = string.Empty;
  public string ThumbnailUrl { get; set; } = string.Empty;
  public long ImageSize { get; set; } = 0L;
 }