asp.net core post api always receive null

Question

Here is my angular 6 code

saveQuestion(value : string) : Observable<string> {
    console.log(value)
    let params = new HttpParams();
    params = params.set('id', value);
    return this._http.post<string>(this.subjectAPi + 'api/Question/Save/', {params});
}

below is my .net core code

[HttpPost("[action]")]
public IActionResult Save([FromBody]string id)
{
    Question ob = new Question();
    ob.update(id)  // id is always null
    return Ok("1");
}

ID is always null. Suggestion will be really appreciated

Answer 1

If I'm not mistaking, ASP.NET Core does not work with camelCasing for JSON by default. Try renaming the id in the HttpParams to be Id .

saveQuestion(value : string) : Observable<string> {
    let params = new HttpParams();
    params = params.set('Id', value);
    return this._http.post<string>(this.subjectAPi + 'api/Question/Save/', {params});
}

Answer 2

The HttpParams is for preparing URL encoded parameters, if you'd like to post a body in JSON you don't need that. Try just simply create your data like:

let body = { id: value }
this._http.post<string>(this.subjectAPi + 'api/Question/Save/', body);

If you really want to post your body as URL encoded data try to set the Content-Type request header:

this._http.post<string>(this.subjectAPi + 'api/Question/Save/', params.toString(), {
    headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
});