JSON Serialize List<KeyValuePair<string, object>>

Question

I used a Dictionary in a Web API project, which is serializing like that in JSON:

{"keyname":{objectvalue},"keyname2:"....

Since I have duplicate keys I could't use Dictionary type any more, and instead now I'm using List<KeyValuePair<string,object>>.

But this is serializing that way:

[{"Key":"keyname","Value":"objectvalue"}...

Is there a way to have the List<KeyValuePair> serialize the same way a dictionary does?

Thanks.

Answer 1

If you use the Newtonsoft Json.NET library you can do the following.

Define a converter to write the list of key/value pairs the way you want:

class MyConverter : JsonConverter
{
    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        List<KeyValuePair<string, object>> list = value as List<KeyValuePair<string, object>>;
        writer.WriteStartArray();
        foreach (var item in list)
        {
            writer.WriteStartObject();
            writer.WritePropertyName(item.Key);
            writer.WriteValue(item.Value);
            writer.WriteEndObject();
        }
        writer.WriteEndArray();
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        // TODO...
    }

    public override bool CanConvert(Type objectType)
    {
        return objectType == typeof(List<KeyValuePair<string, object>>);
    }
}

Then use the converter:

var keyValuePairs = new List<KeyValuePair<string, object>>
                    {
                        new KeyValuePair<string, object>("one", 1),
                        new KeyValuePair<string, object>("two", 2),
                        new KeyValuePair<string, object>("three", 3)
                    };

JsonSerializerSettings settings = new JsonSerializerSettings { Converters = new [] {new MyConverter()} };
string json = JsonConvert.SerializeObject(keyValuePairs, settings);

This generates [{"one":1},{"two":2},{"three":3}]