Mongodb 用 BsonRepresentation(BsonType.ObjectId) vs BsonId vs ObjectId 在 C# 中装饰属性之间的区别

1. If you have a column named Id, id 或 _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 f或 that column. You get a duplicate key err或 exception if trying to insert an item with a key that already exists.

public ObjectId Id {get; set;}

将使用ObjectId的类型生成器

_id: ObjectId("57ade20771e59f422cc652d9")

同样地:

public Guid _id { get; set; }

将使用Guid生成器生成类似smth的

"_id" : BinData(3,"s2Td7qdghkywlfMSWMPzaA==")

还有以下所有属性

public int Id { get; set; }
public string id { get; set; }
public byte[] _id { get; set; }

如果未指定，将使用每种类型的默认值作为索引列.

2. [BsonId]为您提供了任意命名索引的灵活性.

这两个都是索引:

[BsonId] 
public Guid SmthElseOtherThanId { get; set; } 

[BsonId] 
public string StringId { get; set; }

然而

public Guid SmthElseOtherThanId { get; set; } 
public string StringId { get; set; }

不会是索引，mongodb仍将在内部使用_id.

同样的逻辑，

public ObjectId SmthElseOtherThanId {get; set;}

没有[BsonId]个装饰将不会成为索引列.

3. [BsonRepresentation]可以让你在Mongo类型和internal类型之间切换.网络类型，if there's a conversion between them.

有

[BsonId] 
[BsonRepresentation(BsonType.ObjectId)] 
public ObjectId Id { get; set; }

与以下内容相同:

public ObjectId Id { get; set; }

但是

[BsonId] 
[BsonRepresentation(BsonType.ObjectId)] 
public string Id { get; set; }

这是不同的.Mongo将自动生成对象ID，但是您可以在中使用字符串.net、筛选器查询等，因为对象id和字符串之间存在转换.

有

[BsonId] 
[BsonRepresentation(BsonType.ObjectId)] 
public byte[] Id { get; set; }

或

[BsonId] 
[BsonRepresentation(BsonType.ObjectId)] 
public int Id { get; set; }

will fail with a ObjectId not a valid representation f或 a ByteArraySerializer / Int32Serializer message.

但是

[BsonId] 
[BsonRepresentation(BsonType.String)] 
public int StringId { get; set; }

会没事的.