Fetch data for a specific field in Web API C#

Question

Hello,

I have a Json URI which I am using as a data source. I am writing a web api wherein I need to retrieve the data for any of the specific field which user inputs. For e.g, below json is my data source and I need to fetch data only for table_no. So the user will input the field as table_no and the response should only show data with table_no only.

    data": [
    {

            "order": 1,

            "table_no": 94683,

            "table_book_date": "20240103100000",

        },

		{

            "order": 2,

            "table_no": 94544,

            "table_book_date": "20240103100000",

        }

	]
        ```

I have this below C# code but not sure how to use "element" (which is an input for any field (here it is table_no)) to filter my json data source.

```csharp
[HttpGet("[action]/{element}")]
public async Task<IActionResult> Get(string element)
{
    try
    {
      
        var resturantData = await DeSerializeJsonData(element);

        return Ok(new
        {
            resturantData.data
        });
    }
    catch (HttpRequestException httpRequestException)
    {
        return BadRequest($"Error getting info");
    }
}
 private async Task<ResturantData> DeSerializeJsonData(string element)
 {
     using (var client = new HttpClient())
     {
         var response = await client.GetFromJsonAsync<ResturantData>($"<json url>.json");
         return response;
     }
 }

Answer 1

Hi @Abdeali Mandviwala,

You can use JSON.NET to achieve your requirement. Be sure install Microsoft.AspNetCore.Mvc.NewtonsoftJson package If your project version is beyond .NET Core 3.x.

A simple working demo you could follow:

string jsonString = @"{
""data"": [
    {
        ""order"": 1,
        ""table_no"": 94683,
        ""table_book_date"": ""20240103100000""
    },
    {
        ""order"": 2,
        ""table_no"": 94544,
        ""table_book_date"": ""20240103100000""
    }
]
}";

var jsonObject = JsonConvert.DeserializeObject<JObject>(jsonString);

var dataArray = jsonObject["data"] as JArray;

var resultData = new List<object>();
var element = "table_no";
foreach (var item in dataArray)
{
    var tableNo = item[element];
    resultData.Add(new { table_no = tableNo });
}

var resultObject = new { data = resultData };
string resultJson = JsonConvert.SerializeObject(resultObject, Formatting.Indented);

// Print the result
Console.WriteLine(resultJson);

Result:

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Answer 2

(1) The JSON string shown in your post is not correct. Make correction as follows:

{
  "data": [
    {
      "order": 1,
      "table_no": 94683,
      "table_book_date": "20240103100000"
    },
    {
      "order": 2,
      "table_no": 94544,
      "table_book_date": "20240103100000"
    }
  ]
}

(2) Generate the class definition form the JSON string using the "Paste Special" function of the Visual Studio, as shown below:

As for the result, see Rootobject and Datum classes in the sample code shown in step (3) below.

(3) Deserialize the JSON string using the libraries of Newtonsoft.Json or System.Text.Json as shown in the following sample code:

using Newtonsoft.Json;
using System;

namespace ConsoleAppJson
{
    internal class Program
    {
        static void Main(string[] args)
        {
            var path = @"C:\Users\...\Sample.json";  // path to json file
            String jsonString;
            using (var sr = System.IO.File.OpenText(path))
            {
                jsonString = sr.ReadToEnd();
            }

            // Newtonsoft.Json
            var result1 = JsonConvert.DeserializeObject<Rootobject>(jsonString);
            foreach(Datum order in result1.data)
            {
                Console.WriteLine(order.table_no);
            }

            Console.WriteLine("----------------");

            // System.Text.Json
            var result2 = System.Text.Json.JsonSerializer.Deserialize<Rootobject>(jsonString);
            foreach (Datum order in result2.data)
            {
                Console.WriteLine(order.table_no);
            }


            Console.Read();
        }
    }
   
    public class Rootobject
    {
        public Datum[] data { get; set; }
    }

    public class Datum
    {
        public int order { get; set; }
        public int table_no { get; set; }
        public string table_book_date { get; set; }
    }
}

(4) Output is shown below: