Question 247278 in Json Question posted in
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How to check the existence of a JToken key in a JSON object string using C#?

Here is json object as follows:

string jsonString = "{"name":"John","age":30,"city":"New York"}";

I need to know whether it existence of "age" or not.
Please give me ur hand.
I tried a lot, but I couldn’t get I expected.
I have to know whether "age" value is existed on jsonString or not.

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2

Answers


  1. Chosen as BEST ANSWER
    0

    Here's a C# code snippet to check if a key exists in a JSON object string using JSON.NET:

    using Newtonsoft.Json.Linq;

class Program
{
    static void Main(string[] args)
    {
        // Your JSON object string
        string jsonString = "{"name":"John","age":30,"city":"New York"}";

        // Parse the JSON string into a JObject
        JObject jsonObj = JObject.Parse(jsonString);

        // Key to check for existence
        string keyToCheck = "age";

        // Check if the key exists in the JSON object
        bool keyExists = jsonObj.ContainsKey(keyToCheck);

        // Output the result
        if (keyExists)
        {
            Console.WriteLine($"The key '{keyToCheck}' exists in the JSON object.");
        }
        else
        {
            Console.WriteLine($"The key '{keyToCheck}' does not exist in the JSON object.");
        }
    }
}

  2. 0

    To check the existence of a specific key in a JSON object string using C#, you can use the Newtonsoft.Json library (also known as Json.NET), which is a popular JSON parsing library in the .NET ecosystem. Here’s how you can do it:

    First, make sure you have the Newtonsoft.Json library installed in your project. You can install it using NuGet Package Manager or by adding a reference to the Newtonsoft.Json.dll assembly.

    Import the necessary namespace in your C# code:

    using Newtonsoft.Json.Linq;

    Parse the JSON string into a JObject or JToken using JToken.Parse() or JObject.Parse(). Here’s an example with JObject:

    string jsonString = "{"key1": "value1", "key2": "value2", "key3": 
"value3"}";
JObject jsonObject = JObject.Parse(jsonString);

    Check if the key exists in the JSON object using the .ContainsKey() method:

    string keyToCheck = "key2";

if (jsonObject.ContainsKey(keyToCheck))
{
    Console.WriteLine($"The key '{keyToCheck}' exists in the JSON 
    object.");
}
else
{
    Console.WriteLine($"The key '{keyToCheck}' does not exist in the JSON 
    object.");
}
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