Serialize embedded class / object independently or as string?

Question

I am implementing a mongodb cache for this asp.net webapi output cache (I agree redis would be better / faster but for now, I need a mongodb implementation!)

Anyway,

I have a CachedItem class that holds my key / value:

[BsonIgnoreExtraElements]
public class CachedItem
{
    [BsonElement("key")]
    public string Key { get; set; }

    [BsonElement("value")]
    public object Value { get; set; }
}

Value is an object, that could be anything, we don't control that.

In one of my tests, I have a very simple poco:

public class UserFixture
{
    public UserFixture()
    {
        Id = Guid.NewGuid();
    }

    public Guid Id { get; set; }
    public string Name { get; set; }
    public DateTime DateOfBirth { get; set; }
}

When this is set to the Value it is serialized and persisted.

When I try to retrieve it, it fails to deserialize, as it has automatically grabbed the "Id" property.

An error occurred while deserializing the Id property of class WebAPI.OutputCache.MongoDb.Tests.UserFixture: Cannot deserialize Guid from BsonType ObjectId

Obviously, I can't decorate UserFixture

Is there any way I can tell MongoDB driver to basically serialize CachedItem.Value, as say, a string?

I could use JSON.net to do this before saving, and deserialize it on the way back out, but I was hoping to avoid this.

It's also on GitHub That link should take you straight to the relevent commit if you'd like to try the failing test.

I have edited your title. Please see, "Should questions include “tags” in their titles?", where the consensus is "no, they should not". — John Saunders
Cool, although 'serialize' 'class' 'object' and 'string' are all tags on SO too... so I wouldn't be too vigorous on keeping up this best-practice! ;) — Alex

i3arnon i3arnon · Accepted Answer · 2014-02-05T21:28:06

You can of course tell MongoDB to serialize your class as a string by building your own custom BsonSerializer. I have found it easier to inherit from their BsonStringSerializer. You also need to register that serializer with your specific type. (I suggest using a BsonSerializationProvider for that)

What you do need to think about is how to represent all your possible data as a string so you could deserialize it back to your application (Consider for example that you probably need to save the type information).

Serialize embedded class / object independently or as string?

1 Answers