Add a JSON string to an existing one in C#

Question

I'm trying to add a JSON string to an existing one but still haven't been able to do it successfully.

This is the original string: originalJSONString

{
  "properties": [
    "property1",
    "property2"
  ]
}

And I want to add this to the original string: JSONStringIwantToAdd

{
  "filter": {
    "Name": "some filter name",
    "Parameters": {
      "LookupKey": "somekey",
      "LookupValue": "somevalue"
    }
  }
}

To make a resulting string like this: finalJSONString

{
  "properties": [
    "property1",
    "property2"
  ],
  "filter": {
    "Name": "some filter name",
    "Parameters": {
      "LookupKey": "somekey",
      "LookupValue": "somevalue"
    }
  }
}

This is my direction so far but I'm getting null in propertiesJObject and can't figure out afterwards.

Is this even the right direction I'm going?

        var originalJObj = JObject.Parse(originalJSONString);
        var tobeaddedJObj = JObject.Parse(JSONStringIwantToAdd);
        var propertiesJObject = originalJObj["properties"] as JObject;
        propertiesJObject.Add(tobeaddedJObj);
        var serializer = new JsonSerializer { ContractResolver = new CamelCasePropertyNamesContractResolver() };
        var finalJSONString = JObject.FromObject(originalJObj, serializer).ToString();

Can someone please help me with this?

Thank You for your time!

Answer 1

JSON.NET includes functionality to do exactly what you need: JContainer.Merge

Note that Merge modifies the original object, rather than returning a new one:

var original = JObject.Parse(@"{
  ""properties"": [
    ""property1"",
    ""property2""
  ]
}");

var toAdd = JObject.Parse(@"{
  ""filter"": {
    ""Name"": ""some filter name"",
    ""Parameters"": {
      ""LookupKey"": ""somekey"",
      ""LookupValue"": ""somevalue""
    }
  }
}");

original.Merge(toAdd, new JsonMergeSettings
{
    // union array values together to avoid duplicates
    MergeArrayHandling = MergeArrayHandling.Union
});

Fiddle link: https://dotnetfiddle.net/o51GuA

Answer 2

You can do this without explicitly using a serializer.

This code adds the first property from JSONStringIwantToAdd to originalJSONString:

var originalJson = "{\r\n  \"properties\": [\r\n    \"property1\",\r\n    \"property2\"\r\n  ]\r\n}";

var extraJson = "{\r\n  \"filter\": {\r\n    \"Name\": \"some filter name\",\r\n    \"Parameters\": {\r\n      \"LookupKey\": \"somekey\",\r\n      \"LookupValue\": \"somevalue\"\r\n    }\r\n  }\r\n}";

var original = JObject.Parse(originalJson);
var extra = JObject.Parse(extraJson);
var newProperty = extra.Children().First() as JProperty;

original.Add(newProperty.Name, newProperty.Value);

var newJson = original.ToString();

Output:

{
  "properties": [
    "property1",
    "property2"
  ],
  "filter": {
    "Name": "some filter name",
    "Parameters": {
      "LookupKey": "somekey",
      "LookupValue": "somevalue"
    }
  }
}