stream writer is not writing to JSON file in webapi - json

Question

Im trying to write data in a JSON file using webapi but stream writer is not writing data to the file.
JSON File :
{
"Students": [
{
"id": 1,
"name": "Ravi",
"department": "IT"
},
{
"id": 2,
"name": "Raj",
"department": "hr"
},
{
"id": 3,
"name": "avi",
"department": "it"
},
{
"id": 4,
"name": "rome",
"department": "HR"
},
{
"id":5,
"name": "virat",
"department": "HR"
},
{
"id":6 ,
"name": "Tushar",
"department": "RM"
}
]
}
Class
public class Student
{
public int Id { get; set; }
public string Name { get; set; }
public string Department { get; set; }
}
public class Students
{
public List<Student> students { get; set; }
}
Api controller: [HttpPost] method for writing data to the json file.
[Route("api/[controller]")]
[ApiController]
public class StudentsController : ControllerBase
{
[HttpPost]
public IActionResult Add(Students _Student)
{
using (var fs = new FileStream("C:/Users/tanmay_pawar/source/repos/CRUDAPI/CRUDAPI/people.json", FileMode.Append))
using (var sw = new StreamWriter(fs))
{
sw.WriteLine(_Student);
}
}
The data recieved in by _Student is not getting added to the json file.

Answer 1

try this
public IActionResult Add(Students _Student)
{
if(_Student==null || _Student.students==null) return null;
var filePath = #"C:\Users\....\..json";
var json = File.ReadAllText(filePath);
Students students = JsonConvert.DeserializeObject<Students>(json);
students.students.AddRange(_Student.students);
json=JsonConvert.SerializeObject(students);
File.WriteAllText(filePath, json);
}

Answer 2

Try the code like below:
[HttpPost]
public IActionResult Add(Students _Student)
{
string jsonresult = JsonConvert.SerializeObject(_Student);
string path = #"C:\c\people.json";
using(var tw=new StreamWriter(path,true))
{
tw.WriteLine(jsonresult.ToString());
tw.Close();
}
return Ok();
}
result:
Update more picture, add data inside the existing JSON file.