You simply have to replace the value that you want to update. Since StringBuilder has a .Replace inbuilt method, you can implement that method.

 `JArray arr = JArray.Parse(jsonResult.ToString());
 foreach (JObject obj in arr.Children<JObject>())
  {
      foreach(JProperty singleProp in obj.Properties())
      {
        string name = singleProp.Name;
        string value = singleProp.Value.ToString();
                    
        if (name.ToString().Equals("field1")) //good practice
        {
          Int64 newID = 1234;
          jsonResult.Replace(value, newID.ToString());//replacing old value with new value and directly updates jsonResult
        }

      //not necesssary, explanation is given below
        var jsonElement = JsonSerializer.Deserialize<JsonElement>(jsonResult.ToString());
         result = JsonSerializer.Serialize(jsonElement, options);
       }
   }`

And for better formatting, I used JsonSerializer so that your output will look like json object rather than whole string without any lines.

` var options = new JsonSerializerOptions()
                {
                    WriteIndented = true
                };
  var result = ""
  while loop{
     jsonResult.Append(r.GetValue(0).ToString());
     (Above code)
  }
`

I hope this helps.

You simply have to replace the value that you want to update. Since StringBuilder has a .Replace inbuilt method, you can implement that method.

 `JArray arr = JArray.Parse(jsonResult.ToString());
 foreach (JObject obj in arr.Children<JObject>())
  {
      foreach(JProperty singleProp in obj.Properties())
      {
        string name = singleProp.Name;
        string value = singleProp.Value.ToString();
                    
        if (name.ToString().Equals("field1")) //good practice
        {
          Int64 newID = 1234;
          jsonResult.Replace(value, newID.ToString());//replacing old value with new value and directly updates jsonResult
        }

      //not necesssary, explanation is given below
        var jsonElement = JsonSerializer.Deserialize<JsonElement>(jsonResult.ToString());
         result = JsonSerializer.Serialize(jsonElement, options);
       }
   }`

And for better formatting, I used JsonSerializer so that your output will look like json object rather than whole string without any lines.

` var options = new JsonSerializerOptions()
                {
                    WriteIndented = true
                };
  var result = ""
  while loop{
     jsonResult.Append(r.GetValue(0).ToString());
     (Above code)
  }
`