CODEWITHSUNDEEP
c#mongodb
EugeneK
EugeneK

Reputation: 2224

How to update a generic type with MongoDB C# driver in MongoDB 2.7

Following code from this question How to update a generic type with MongoDB C# driver no longer works, how to do the same in MongoDB 2.7?

void Update(T entity)
{
    collection.Save<T>(entity);
}

Upvotes: 1

Views: 2138

Answers (1)

mickl
mickl

Reputation: 49975

Currently Save is only available in legacy MongoDB C# driver. You can find unresolved ticket with discussion on driver JIRA.

It's still possible to implement something similar in C#. The behavior is documented here:

If the document does not contain an _id field, then the save() method calls the insert() method. During the operation, the mongo shell will create an ObjectId and assign it to the _id field.

and

If the document contains an _id field, then the save() method is equivalent to an update with the upsert option set to true and the query predicate on the _id field.

So you can introduce marker interface in C# to represent _id field:

public interface IIdentity
{
    ObjectId Id { get; set; }
}

and then you can implement Save like this:

public void Update<T>(T entity) where T : IIdentity
{
    if(entity.Id == ObjectId.Empty)
    {
        collection.InsertOne(entity); // driver creates _id under the hood
    }
    else
    {
        collection.ReplaceOne(x => x.Id == entity.Id, entity, new UpdateOptions() { IsUpsert = true } );
    }
}

or simpler:

public void Update<T>(T entity) where T : IIdentity
{
    if(entity.Id == ObjectId.Empty)
    {
        entity.Id = ObjectId.GenerateNewId();
    }
    collection.ReplaceOne(x => x.Id == entity.Id, entity, new UpdateOptions() { IsUpsert = true } );
}

Upvotes: 2

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