Updating property of specific collection item with FindAndModify

Question

Post class:

public class Post
{
    [BsonRepresentation(BsonType.ObjectId)]
    public string Id { get; set; } 
    [BsonRepresentation(BsonType.ObjectId)]
    public string CreatorId { get; set; }
    public string CreatorName { get; set; }
    public string Text { get; set; }
    public bool IsPublic { get; set; }
    public ICollection<Comment> Comments { get; set; }
    public DateTime CreationDate { get { return ObjectId.Parse(Id).CreationTime; } }
    public DateTime? DeletionDate { get; set; }
}

Comment class:

public class Comment
{
    [BsonRepresentation(BsonType.ObjectId)]
    public string Id { get; set; }
    [BsonRepresentation(BsonType.ObjectId)]
    public string CreatorId { get; set; }
    public string CreatorName { get; set; }
    public string Text { get; set; }
    public DateTime CreationDate { get { return ObjectId.Parse(Id).CreationTime; } }
    public DateTime? DeletionDate { get; set; }
}

I would like to find set the DeletionDate property of a Comment inside a Post.Comments given that Comment.Id and Comment.CreatorId equals the given parameters.

How can I do this?

Answer 1

I solved it with the following:

var query = Query<Post>.ElemMatch(p => p.Comments, builder => 
    builder.And(
        Query<Comment>.EQ(c => c.Id, commentId),
        Query<Comment>.EQ(c => c.CreatorId, creatorId)));

var update = Update.Set("Comments.$.DeletionDate", DateTime.UtcNow);

var args = new FindAndModifyArgs
{
    Query = query,
    Update = update
};

var result = _db.Posts.FindAndModify(args);