Convert nested JSON to simple JSON

Question

I'm trying to convert a nested json to simple json by recursively traversing. (Structure of input json is unknown)

for example, I want json like this

{
    "FirstName": "Rahul",
    "LastName": "B",
    "EmpType": {
        "RID": 2,
        "Title": "Full Time"
    },
    "CTC": "3.5",
    "Exp": "1",
    "ComplexObj": {
        "RID": 3,
        "Title": {
            "Test": "RID",
            "TWO": {
                "Test": 12
            }
        }
    }
}

to be converted something like this

{
    "FirstName": "Rahul",
    "LastName": "B",
    "EmpType__RID": 2,
    "EmpType__Title": "Full Time",
    "CTC": "3.5",
    "Exp": "1",
    "ComplexObj__RID": 3,
    "ComplexObj__Title__Test": "RID",
    "ComplexObj__Title__TWO__Test": 12
}

each fields in nested object will be changed to key which represents its actual path.

this is what I have done so far.

    public static void ConvertNestedJsonToSimpleJson(JObject jobject, ref JObject jobjectRef, string currentNodeName = "", string rootPath = "")
    {
        string propName = "";
        if (currentNodeName.Equals(rootPath))
        {
            propName = currentNodeName;
        }
        else
        {
            propName = (rootPath == "" && currentNodeName == "") ? rootPath + "" + currentNodeName : rootPath + "__" + currentNodeName;
        }

        foreach (JProperty jprop in jobject.Properties())
        {
            if (jprop.Children<JObject>().Count() == 0)
            {
                jobjectRef.Add(propName == "" ? jprop.Name : propName + "__" + jprop.Name, jprop.Value);
            }
            else
            {
                currentNodeName = jprop.Name;
                rootPath = rootPath == "" ? jprop.Name : rootPath;
                ConvertNestedJsonToSimpleJson(JObject.Parse(jprop.Value.ToString()), ref jobjectRef, currentNodeName, rootPath);
            }
        }
    }

and getting wrong result

{
    "FirstName": "Rahul",
    "LastName": "B",
    "EmpType__RID": 2,
    "EmpType__Title": "Full Time",
    "CTC": "3.5",
    "Exp": "1",
    "EmpType__ComplexObj__RID": 3,
    "EmpType__Title__Test": "RID",
    "EmpType__two__Test": 12
}

will appreciate any help on correcting my code, or any other approach to archive this.

Answer 1

• You don't need to convert the value of the property to string and then parse it again every time - just cast it to JObject
• You don't need the complicated conditional logic to generate the name of the property - just use this: prefix + jprop.Name + "__"

The code:

public static void FlattenJson(JObject node, JObject result, string prefix = "")
{
    foreach (var jprop in node.Properties())
    {
        if (jprop.Children<JObject>().Count() == 0)
        {
            result.Add(prefix + jprop.Name, jprop.Value);
        }
        else
        {
            FlattenJson((JObject)jprop.Value, $"{prefix}{jprop.Name}__", result);
        }
    }
}

You can call it like this:

var node = JObject.Parse(/* the input string */);
var result = new JObject();
FlattenJson(node, result);

Answer 2

Your problem is in the line rootPath = rootPath == "" ? jprop.Name : rootPath;. You are changing the rootPath when you first come across EmpType which means when you process ComplexObj your rootPath is wrong. What I believe you intended is just to change what you were passing into the recursive function.

As it is though it is unnecessary to keep track of root and currentnode as two separate items. Better would be to just track the current prefix for a given node in code that looks more like this:

public static void ConvertNestedJsonToSimpleJson(JObject input, JObject output, string prefix = "")
{
    foreach (JProperty jprop in input.Properties())
    {
        var name = prefix==""?jprop.Name:String.Format("{0}__{1}", prefix,jprop.Name);
        if (jprop.Children<JObject>().Count() == 0)
        {
            output.Add(name, jprop.Value);
        }
        else
        {
            ConvertNestedJsonToSimpleJson((JObject)jprop.Value, output, name);
        }
    }
}

This now gives me the output:

{
  "FirstName": "Rahul",
  "LastName": "B",
  "EmpType__RID": 2,
  "EmpType__Title": "Full Time",
  "CTC": "3.5",
  "Exp": "1",
  "ComplexObj__RID": 3,
  "ComplexObj__Title__Test": "RID",
  "ComplexObj__Title__TWO__Test": 12
}

which looks correct.

Answer 3

Could you do something like this using linq

var jsonObj = jobject.select(x => new CustomJson {
   FirstName = x.FirstName,
   LastName = x.LastName,
   EmpTypeId = x.EmpType.Id,
   Title = x.EmpType.Title
   etc etc
});