public ObjectId Id {get; set;}
//or
[BsonId]
public string Id {get; set;}
//or
[BsonId]
[BsonRepresentation(BsonType.ObjectId)]
public string Id {get; set;}
//or
[BsonId]
[BsonRepresentation(BsonType.String)]
public string Id {get; set;}
字段映射
ID
the Id property:
Is required for mapping the Common Language Runtime (CLR) object to the MongoDB collection.
If you have a column named Id, id or _id, in your strongly typed TDocument class (the item type in a collection), then a column named "_id" will be generated in Mongo. It will also create an index for that column. You get a duplicate key error exception if trying to insert an item with a key that already exists.
MongoDB 数据集中存放的数据，称之为文档（Document）。每个文档在存放时，都需要有一个ID，而这个 ID 的名称，固定叫 _id，类型是 MongoDB.Bson.ObjectId。
当建立映射时，如果给出 _id 字段，则 MongoDB 会采用这个 ID 做为这个文档的 ID ，如果不给出，MongoDB 会自动添加一个 _id 字段。在使用上是完全一样的。唯一的区别是，如果映射类中不写 _id，则 MongoDB 自动添加 _id 时，会用 ObjectId 作为这个字段的数据类型。
ObjectId 是一个全局唯一的数据。
MongoDB 允许使用其它类型的数据作为 ID，例如：string，int，long，GUID 等，但这就需要你自己去保证这些数据不超限并且唯一。
BsonId属性
1.the Id property Is annotated with [BsonId] to designate this property as the document's primary key
2.ObjectId 别名：可以在类中修改 _id 名称为别的名称，但需要加一个描述属性 BsonId，BsonId 属性会告诉映射，topic_id 就是这个文档数据的ID 。MongoDB在保存时，会将这个 topic_id 转成 _id 保存到数据集中。
BsonRepresentation属性
[BsonRepresentation] lets you juggle with the Mongo type vs the internal .Net type, if there's a conversion between them.
用来在映射类中的数据类型和数据集中的数据类型做转换。
the Id property Is annotated with [BsonRepresentation(BsonType.ObjectId)] to allow passing the parameter as type string instead of an ObjectId structure. Mongo handles the conversion from string to ObjectId.
using MongoDB.Bson;
using MongoDB.Bson.Serialization.Attributes;
namespace Nop.Core
{
public abstract class ParentEntity
{
//[BsonId] to designate this property as the document's primary key.
[BsonId]
// [BsonRepresentation(BsonType.ObjectId)] to allow passing the parameter as type string instead of an ObjectId structure.
//Mongo handles the conversion from string to ObjectId.
[BsonRepresentation(BsonType.ObjectId)]
public string _id { get; set; }
}
}Select a specifid "Id" and add it the url, i.e.
http://localhost:5004/api/speaker/54b7d51140c10266ffa3b04d and a single item is returned.
{
"_id": "54b7d51140c10266ffa3b04d", <---here is _id
"First": "Shayne",
"Last": "Boyer",
"Twitter": "@spboyer",
"Title": "Developer Guy",
"Blog": "tattoocoder.com"
}在类中修改 _id 名称为别的名称
using MongoDB.Bson;
using MongoDB.Bson.Serialization.Attributes;
namespace Nop.Core
{
public abstract class ParentEntity
{
[BsonId] //[BsonId] to designate this property as the document's primary key.
[BsonRepresentation(BsonType.ObjectId)] // [BsonRepresentation(BsonType.ObjectId)] to allow passing the parameter as type string instead of an ObjectId structure. Mongo handles the conversion from string to ObjectId.
public string Id { get; set; } //可以在类中修改 _id 名称为别的名称，但需要加一个描述属性 BsonId，BsonId 属性会告诉映射，topic_id 就是这个文档数据的ID 。MongoDB在保存时，会将这个 topic_id 转成 _id 保存到数据集中。
}
}Select a specifid "Id" and add it the url, i.e.
http://localhost:5004/api/speaker/54b7d51140c10266ffa3b04d and a single item is returned.
{
"Id": "54b7d51140c10266ffa3b04d", <---here is Id
"First": "Shayne",
"Last": "Boyer",
"Twitter": "@spboyer",
"Title": "Developer Guy",
"Blog": "tattoocoder.com"
}
https://syxdevcode.github.io/2020/09/28/MongoDB%20Dotnet%20Core%E6%95%B0%E6%8D%AE%E6%98%A0%E5%B0%84/