Returns messages record exist or insert from MVC to Angular

Dear all,

I am beginner in ASP .net MVC and Angular 5. I was trying to insert record using Angular 5 to MVC using API Controller.

Here is my TypeScript file code

saveStudent(Student){
let headers = new Headers();
headers.append('Content-Type', 'application/json');
headers.append('Access-Control-Allow-Origin', '*');
headers.append('Access-Control-Allow-Methods', 'GET, POST, PUT');
return this.http.post(environment.apiUrl + 'Student', Student, { headers: headers })
.pipe(map(data => data.json()),
catchError((error: any) => {
throw error;
}));
}

Above code get redirected to StudentController which is inherited from ApiController.

There is post method which has return type of void as follows :-

There is interface with name IStudentRepository which contains post as follows : -

There is StudentRepository which contains following :-

public void Post(Student objstudent)
{
string message = string.Empty;
string query = "select count(*) from mststundent where StudentName = " + objclass.StudentName;
MySqlConnection conn = new MySqlConnection(ConnStr);
conn.Open();
MySqlCommand objcmd = new MySqlCommand(query);
int result = Convert.ToInt32(objcmd.ExecuteScalar());
if (result > 0)
{
message = "Exist";
}
else
{
message = "Inserted";
}
conn.Close();
}

what I want to do is return those messages.

Please let me anyone have easy solution.

Thanking You in adnavce.