C# – Read and parse a Json File in C#

c++jsonlarge-filesparsing

I have spent the best part of two days "faffing" about with code samples and etc., trying to read a very large JSON file into an array in c# so I can later split it up into a 2d array for processing.

The problem I was having was I could not find any examples of people doing what I was trying to do. This meant I was just editing code a little an hoping for the best.

I have managed to get something working that will:

  • Read the file Miss out headers and only read values into array.
  • Place a certain amount of values on each line of an array. (So I
    could later split it an put into 2d array)

This was done with the code below but it crashes the program after entering a few lines into the array. This might have to do with the file size.

// If the file extension was a jave file the following 
// load method will be use else it will move on to the 
// next else if statement
if (fileExtension == ".json") 
{
    int count = 0;
    int count2 = 0;
    int inOrOut = 0;
    int nRecords=1; 
    JsonTextReader reader = new JsonTextReader(new StreamReader(txtLoaction.Text));
    string[] rawData = new string[5];
    while (reader.Read())
    {
        if (reader.Value != null)
            if (inOrOut == 1)
            {
                if (count == 6)
                {
                    nRecords++;
                    Array.Resize(ref rawData, nRecords);
                    //textBox1.Text += "\r\n";
                    count = 0;
                }
                rawData[count2] += reader.Value + ","; //+"\r\n"
                inOrOut = 0;
                count++;
                if (count2 == 500)
                {
                    MessageBox.Show(rawData[499]);
                }
            }
            else
            {
                inOrOut = 1;
            }
    } 
}

A snippet of the JSON I am working with is:

[ 
    { "millis": "1000", 
      "stamp": "1273010254", 
      "datetime": "2010/5/4 21:57:34", 
      "light": "333", 
      "temp": "78.32", 
      "vcc": "3.54" }, 
] 

I need the values out of this JSON. For example, I need "3.54", but I would not want it to print the "vcc".

I am hoping someone can show me how to read a JSON file in and only extract the data that I need and put it into an array or something that I can use to later put into an array.

Best Solution

How about making everything easier with Json.NET?

    public void LoadJson()
    {
        using (StreamReader r = new StreamReader("file.json"))
        {
            string json = r.ReadToEnd();
            List<Item> items = JsonConvert.DeserializeObject<List<Item>>(json);
        }
    }

    public class Item
    {
        public int millis;
        public string stamp;
        public DateTime datetime;
        public string light;
        public float temp;
        public float vcc;
    }

You can even get the values dynamically without declaring Item class.

    dynamic array = JsonConvert.DeserializeObject(json);
    foreach(var item in array)
    {
        Console.WriteLine("{0} {1}", item.temp, item.vcc);
    }