Serializing an array of objects one at a time using JSON.NET

Question

I am trying to serialize multiple elements in json and format them as an array.

This event is based on a set of data that cannot be stored in memory as a whole collection. But I need to serialize each element to a file and format it as an array.

_jsonWriter = new JsonTextWriter(new StreamWriter("Output.json")));
DataGatherer.ItemGathered += item =>
{
    _jsonSerializer.Serialize(_jsonWriter, item);
    _jsonWriter.Flush();
};

Currently, the following outputs:

{
  "Id": 218515,
  "Name": "A"
}{
  "Id": 118647,
  "Name": "B"
}

Since the serializer serializes each element as an object, it does not know its array.

So, how can I say that the JSON.Net serializer treats each element as an array element and formats the data as follows:

[{ "Id": 218515, "Name": "A"},{"Id": 118647,"Name": "B"}]

Thanks for any tips!

Answer 1

JsonItemWriter, JsonTextWriter. , - . , JsonTextWriter StartArray . ItemWriter , EndArray . , ItemWriter JsonTextWriter.

JsonItemWriter:

class JsonItemWriter
{
    private JsonTextWriter innerWriter;
    private JsonSerializer serializer;

    public JsonItemWriter(JsonTextWriter innerWriter, JsonSerializer serializer)
    {
        this.innerWriter = innerWriter;
        this.serializer = serializer;
    }

    public void WriteItem(object item)
    {
        if (innerWriter.WriteState == Newtonsoft.Json.WriteState.Start)
        {
            innerWriter.WriteStartArray();
        }
        serializer.Serialize(innerWriter, item);
        innerWriter.Flush();
    }

    public void Close()
    {
        innerWriter.WriteEndArray();
        innerWriter.Close();
    }
}

:

_jsonWriter = new JsonTextWriter(new StreamWriter("Output.json"));
_itemWriter = new JsonItemWriter(_jsonWriter, _jsonSerializer);

DataGatherer.ItemGathered += item =>
{
    _itemWriter.WriteItem(item);
};

, DataGatherer :

class Program
{
    static void Main(string[] args)
    {
        JsonSerializer jsonSerializer = new JsonSerializer();
        JsonTextWriter jsonWriter = new JsonTextWriter(new StreamWriter("Output.json"));
        JsonItemWriter itemWriter = new JsonItemWriter(jsonWriter, jsonSerializer);

        MockDataGatherer gatherer = new MockDataGatherer();
        gatherer.ItemGathered += item =>
        {
            itemWriter.WriteItem(item);
        };

        var items = new[]
        {
            new { Id = 218515, Name = "A" },
            new { Id = 118647, Name = "B" }
        };
        gatherer.SimulateReceivingItems(items);

        itemWriter.Close();

        using (StreamReader reader = new StreamReader("Output.json"))
        {
            Console.WriteLine(reader.ReadToEnd());
        }
    }
}

class MockDataGatherer
{
    public void SimulateReceivingItems(IEnumerable<object> items)
    {
        foreach (object item in items)
        {
            ItemGathered(item);
        }
    }

    public event ItemGatheredEventHandler ItemGathered;
    public delegate void ItemGatheredEventHandler(object item);
}

( , ):

[{"Id":218515,"Name":"A"},{"Id":118647,"Name":"B"}]

Answer 2

IEnumerable<YourObject>. , serialiazer, . ItemGathered yield return