Setting a custom json converter for DocumentDb

Question

I am using a typed DocumentQuery to read documents from a collection of an Azure DocumentDb.

from f in client.CreateDocumentQuery<MyModel>(Collection.SelfLink) select f

Because I do not find a way how I can set the neccesarry custom json converter, it throws this exeption:

Could not create an instance of type AbstractObject. Type is an interface or abstract class and cannot be instantiated.

Usually you do something like this to make it work:

var settings = new JsonSerializerSettings();
settings.Converters.Add(new MyAbstractConverter());
client.SerializerSettings = settings;

DocumentClient doesn't have any SerializerSettings. So the question is, how can I tell the DocumentDB client that it must use a custom converter when deserializing the json data to my model?

Have you tried adding a `[JsonConverter(typeof(MyAbstractConverter))]` attribute to your abstract model class? — Brian Rogers, Dec 11 '14 at 22:35
The Attribute works :) I am getting another exeption, but this is not about the abstract instance. Thank you! — dixus, Dec 12 '14 at 06:39

score 5 · Accepted Answer · answered Sep 18 '15 at 18:18

You can add [JsonConverter(typeof(MyAbstractConverter))] to your model class.

Here's an example model class with custom Json settings:

namespace DocumentDB.Samples.Twitter
{
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using DocumentDB.Samples.Shared.Util;
    using Newtonsoft;
    using Newtonsoft.Json;

    /// <summary>
    /// Represents a user.
    /// </summary>
    public class User
    {
        [JsonProperty("id")]
        public long UserId { get; set; }

        [JsonProperty("name")]
        public string Name { get; set; }

        [JsonProperty("screen_name")]
        public string ScreenName { get; set; }

        [JsonProperty("created_at")]
        [JsonConverter(typeof(UnixDateTimeConverter))]
        public DateTime CreatedAt { get; set; }

        [JsonProperty("followers_count")]
        public int FollowersCount { get; set; }

        [JsonProperty("friends_count")]
        public int FriendsCount { get; set; }

        [JsonProperty("favourites_count")]
        public int FavouritesCount { get; set; }
    }
}

Sorry, should have provided a link earlier: https://github.com/Azure/azure-documentdb-dotnet/blob/master/samples/code-samples/Shared/Util/UnixDateTimeConverter.cs — Andrew Liu, Apr 13 '16 at 00:37
@AndrewLiu what does that attribute actually do, does it add things to the serialised file in DocumentDb? — m1nkeh, Jan 23 '18 at 21:16

score 3 · Answer 2 · answered Aug 15 '17 at 14:39

3

The latest CosmosDB SDK now includes support for JsonSerializerSettings so you don't have to use JsonConverter anymore, you can use your own ContractResolver. See related SO post.

answered Aug 15 '17 at 14:39

SliverNinja - MSFT

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Setting a custom json converter for DocumentDb

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