使用MongoDB .Net驱动程序查找POCO

Question

MongoDB比我想起的要难！我已经尝试了各种版本的if-exists-replace-else-insert以及各种功能和选项。它应该很容易，不是吗？

这是我个人认为，以下应该工作。

var collection = storageClient.GetCollection<Observer>("observers"); 
await collection.Indexes.CreateOneAsync(Builders<Observer>.IndexKeys.Ascending(_ => _.MyId), new CreateIndexOptions { Unique = true }); 

foreach (var observer in _observers) 
{ 
    observer.Timestamp = DateTime.Now; 

    var res = await collection.FindAsync(o => o.MyId == observer.MyId); 
    if (res==null ||res.Current == null) { 
     await collection.InsertOneAsync(observer); //Part 1, fails 2nd time solved with res.MoveNextAsync() 
    } 
    else 
    { 
      observer.ID = res.Current.Single().ID; 
      var res2 = await collection.ReplaceOneAsync(o=>o.MyId==observer.MyId, observer); 

      var res3 = await collection.FindAsync(o => o.MyId == observer.MyId); 
      await res3.MoveNextAsync(); 
      Debug.Assert(res3.Current.Single().Timestamp == observer.Timestamp); //Part 2, Assert fails. 
    } 
} 

观察看起来大约是这样的：

public class Observer : IObserver 
{ 
    [BsonId] 
    public Guid ID { get; set; } 

    public int MyId { get; set; } 

    public DateTime Timestamp { get; set; } 
} 

我使用完全相同的集合运行此第二次，我意外地得到：

E11000 duplicate key error index: db.observers.$MyId_1 dup key: { : 14040 } 

编辑：

新增原第二部分代码：替换。

编辑2：

现在我的代码看起来像这样。仍然失败。

var collection = storageClient.GetCollection<Observer>("gavagai_mentions"); 
    await collection.Indexes.CreateOneAsync(Builders<Observer>.IndexKeys.Ascending(_ => _.MyID), new CreateIndexOptions { Unique = true }); 
    foreach (var observer in _observers) 
    { 
    observer.Timestamp = DateTime.Now; 

    // Create a BsonDocument version of the POCO that we can manipulate 
    // and then remove the _id field so it can be used in a $set. 
    var bsonObserver = observer.ToBsonDocument(); 
    bsonObserver.Remove("_id"); 

    // Create an update object that sets all fields on an insert, and everthing 
    // but the immutable _id on an update. 
    var update = new BsonDocument("$set", bsonObserver); 
    update.Add(new BsonDocument("$setOnInsert", new BsonDocument("_id", observer.ID))); 

    // Enable the upsert option to create the doc if it's not found. 
    var options = new UpdateOptions { IsUpsert = true }; 
    var res = await collection.UpdateOneAsync(o => o.MyID == observer.MyID, 
          update, options); 


    var res2 = await collection.FindAsync(o => o.MyID == observer.MyID); 
    await res2.MoveNextAsync(); 
    Debug.Assert(res2.Current.Single().Timestamp == observer.Timestamp); //Assert fails, but only because MongoDB stores dates as UTC, or so I deduce. It works!! 
    } 

Answer 1

如果文档不存在，您可以使用IsUpsert选项创建文档，以UpdateOneAsync自动完成。

foreach (var observer in _observers) 
{ 
    // Create a BsonDocument version of the POCO that we can manipulate 
    // and then remove the _id field so it can be used in a $set. 
    var bsonObserver = observer.ToBsonDocument(); 
    bsonObserver.Remove("_id"); 

    // Create an update object that sets all fields on an insert, and everthing 
    // but the immutable _id on an update. 
    var update = new BsonDocument("$set", bsonObserver); 
    update.Add(new BsonDocument("$setOnInsert", new BsonDocument("_id", observer.ID))); 

    // Enable the upsert option to create the doc if it's not found. 
    var options = new UpdateOptions { IsUpsert = true };  
    var res = await collection.UpdateOneAsync(o => o.MyId == observer.MyId, 
               update, options); 
} 

Answer 2

好的，这是我用光标工作了很长一段时间。

await res.MoveNextAsync(); 

帮助。

这件事对Google来说并不难，但事实是，我失败了，所以我要离开这个问题了。

如果你有第二部分https://stackoverflow.com/questions/32586064/replace-poco-with-mongodb-net-driver-2的答案，那么，真的很想在这里发布，那么我会很高兴两个编辑问题。

正如在评论中指出的那样，信息实际上在文档http://mongodb.github.io/mongo-csharp-driver/2.0/reference/driver/crud/reading/#finding-documents中很容易获得。