How to add properties at runtime to JSON (C#)

Question

Note: Im working with System.Text.Json package Below is JSON I am getting from a database. I have to go through each of the keys in the JSON and check if there is a period (

Answer 1

I was having similar issue, and have found a solution, see below the code and comments. I am using Newtonsoft though but it is worth checking if you can use Newtonsoft library and have not found a solution for System.Text.Json.

All controls in your JSON are part of component object/array so we can use JSONPath, see the link for more details.

public void IterateJson(JObject obj, string mandatoryFieldKey)
        {
JToken jTokenFoundForMandatoryField = obj.SelectToken
("$..components[?(@.key == '" + mandatoryFieldKey + "')]");   
            //Now we convert this oken into an object so that we can add properties/objects in it
            if (jTokenFoundForMandatoryField is JObject jObjectForMandatoryField)
            {
                //We check if validate already exists for this field, if it does not
 //exists then we add validate and required property inside the if condition
                if (jObjectForMandatoryField["validate"] == null)
                    jObjectForMandatoryField.Add("validate", 
JObject.FromObject(new { required = true })); //add validate and required property
                else
                {
                    //If validate does not exists then code comes here and 
//we convert the validate into a JObject using is JObject statement
                    if (jObjectForMandatoryField["validate"] is JObject validateObject)
                    {
                        //We need to check if required property already exists, 
//if it does not exists then we add it inside the if condition.
                        if (validateObject["required"] == null)
                        {
                            validateObject.Add("required", true); //add required property
                        }
                    }
                }                
            }  
}   

Answer 2

It was interesting task for me, so this is what i have written

class Program
{
    static void Main(string[] args)
    {
        string jsonFilePath = @"test.json"; //path to your json
        string json = File.ReadAllText(jsonFilePath);
        var data = JObject.Parse(json);
        CheckJson(data);
        Console.ReadLine();
    }

    static void CheckJson(JToken value)
    {
        if (value.Values().Count() != 0) //if more than 0 - so value is object or array and we have to call this method for each property
        {
            foreach (var item in value.Values().ToList())
            {
                CheckJson(item);
            }
        }
        else if (true) //else - we have exactly value of key, which we can check, for example if . exists or additional checks
        {
            if (value.Parent.Parent is JObject jObject && jObject["validate"] == null) //check if above "required" property exists 
            {
                jObject.Add("validate", JObject.FromObject(new { required = true })); //add required property
            }
        }

    }
}

This code will add in each object property "required" if it is not exists. All you need - just add Validation method and call it in if block. And better to add additional validation that won't continue checking all properties if "required" property exists

Answer 3

One of the options would be to parse json into JObject and add property to it via Newtonsoft's Json.NET:

var obj = JObject.Parse("{'key':'value'}");
obj.Add("required", true);
Console.WriteLine(obj); // { "key": "value", "required": true }

To add new object you can use this overload of Add:

obj.Add("validate", JObject.FromObject(new { required = true }));

So the whole solution will look something like this:

var obj = JObect.Parse(your_json);

foreach(var token in obj.DescendantsAndSelf().ToList()) // ToList is important!!!
{
    if(token is JObject xObj)
    {
        // check your conditions for adding property
        // check if object does not have "validate" property
        if(satisfies_all_conditions)
        {
            xObj.Add("validate", JObject.FromObject(new { required = true }));
        }
    }
}