How to GET JSON data from an API using C#

A guide on how to retrieve JSON data from an API using C#, leveraging the HttpClient class and Newtonsoft.Json library for processing data.

In this article, we will explore how to make a GET request to an API and retrieve JSON data using C#. We will use the HttpClient class to send the request and Newtonsoft.Json to parse the data.

using System;
using System.Net.Http;
using System.Threading.Tasks;
using Newtonsoft.Json;

namespace GetJsonDataFromApi
{
    class Program
    {
        static async Task Main(string[] args)
        {
            string url = "https://api.example.com/data"; // Change URL to actual API
            using HttpClient client = new HttpClient();
            var response = await client.GetAsync(url);

            if (response.IsSuccessStatusCode)
            {
                string jsonData = await response.Content.ReadAsStringAsync();
                var data = JsonConvert.DeserializeObject<YourDataType>(jsonData);
                Console.WriteLine(JsonConvert.SerializeObject(data, Formatting.Indented));
            }
            else
            {
                Console.WriteLine($"Error: {response.StatusCode}");
            }
        }
    }

    public class YourDataType
    {
        // Define properties corresponding to the JSON structure here
    }
}

Detailed Explanation

1. using System;: Imports the System namespace, containing fundamental classes.
2. using System.Net.Http;: Imports the System.Net.Http namespace to use HttpClient.
3. using System.Threading.Tasks;: Imports the System.Threading.Tasks namespace to support asynchronous programming.
4. using Newtonsoft.Json;: Imports the Newtonsoft.Json namespace to use the JSON library.
5. static async Task Main(string[] args): The asynchronous Main method, the entry point of the program.
6. string url = "https://api.example.com/data";: The URL of the API to access.
7. using HttpClient client = new HttpClient();: Initializes an HttpClient object to send HTTP requests.
8. var response = await client.GetAsync(url);: Sends a GET request to the URL and awaits the response.
9. if (response.IsSuccessStatusCode): Checks if the request was successful.
10. string jsonData = await response.Content.ReadAsStringAsync();: Reads the response content and converts it to a JSON string.
11. var data = JsonConvert.DeserializeObject<YourDataType>(jsonData);: Parses the JSON string into a defined data type.
12. Console.WriteLine(JsonConvert.SerializeObject(data, Formatting.Indented));: Prints the parsed data in a formatted style.
13. else { Console.WriteLine($"Error: {response.StatusCode}"); }: Prints the error code if the request was unsuccessful.

System Requirements

• .NET Core 3.1 or .NET 5.0 or later
• Libraries: Newtonsoft.Json

How to install the libraries needed to run the C# code above

Use the NuGet Package Manager to install Newtonsoft.Json:

Install-Package Newtonsoft.Json

Tips

• Ensure that the API URL you are using is accurate and accessible.
• Check if the API requires authentication and handle that if necessary.