Linq到带有where子句的json过滤结果

Question

I'm new to json. I'm trying to filter json data using linq to json query in C#. I'm trying to retrieve multiple values from json data:

string json= @"{
 "parts": [
    {

      "attributes": {
        "Motherboard": "Gigabyte GA-H81M-S2H",
        "Max RAM": "16GB",
        "Form Factor": "Micro ATX",
        "RAM Slots": 2,
        "Socket / CPU": "LGA1150"
      },
      "type": "Motherboard",
      "name": "Gigabyte GA-H81M-S2H",
      "slug": "gigabyte-motherboard-gah81ms2h"
    },
    {
        "attributes": {
        "Motherboard": "MSI H55-G43",
        "Max RAM": "16GB",
        "Form Factor": "ATX",
        "RAM Slots": 4,
        "Socket / CPU": "LGA1156"
      },
      "type": "Motherboard",
      "name": "MSI H55-G43",
      "slug": "msi-motherboard-h55g43"
    },
    {
      "url": "http://pcpartpicker.com/part/asus-motherboard-rampageivblackedition",
      "attributes": {
        "Motherboard": "Asus Rampage IV Black Edition",
        "Max RAM": "128GB",
        "Form Factor": "EATX",
        "RAM Slots": 8,
        "Socket / CPU": "LGA2011"
      },
      "type": "Motherboard",
      "name": "Asus Rampage IV Black Edition",
      "slug": "asus-motherboard-rampageivblackedition"
    }
 ],

}";

This is my C# code:

JObject results = JObject.Parse(json);
  var categories = from c in results["parts"]["attributes"].Children()["Motherboard"].Values<string>()
                         group c by c
                         into g
                         orderby g.Count() descending
                         select new { Category = g.Key, Count = g.Count() };

I tried with this code and it not returns any result.Please let me know where I'm doing mistake or is this the proper way to write the query.Can anyone please help me to solve this.

Answer 1

You can use SelectTokens for queries of this nature. It supports JSONPath query syntax. Thus:

        var categories = from c in results.SelectTokens("parts[*].attributes.Motherboard")
                         group c by c
                             into g
                             orderby g.Count() descending
                             select new { Category = (string)g.Key, Count = g.Count() };

In your JSON, the value of "parts" : [...] is an array; in the query, "parts[*]" is a wildcard that searches through all elements of the array.