angular2 cannot access to this in the class angular2

when i need to access to this ,

but i found problem to give the value true to this.idHiden

like : this.idHiden = true the error :

TypeError: Cannot set property 'idHiden' of null

and the code

import { Component  , Output} from '@angular/core' ;
import { NgForm }     from '@angular/forms';
 import * as Datastore from 'nedb';

@Component({
  moduleId : module.id ,
  providers: [ ],
  templateUrl : 'info.component.html'
})

export class InfoComponent {
  selkName : any ;
  insertedSelk : any  ;
  idHiden : false ;

  selkValidate : number ;

  constructor(){
    this.selkName = '' ;
    this.insertedSelk =  [] ;
    this.selkValidate = 1 ;
    this.SelkFinde(this) ;

  }
  DeletSelk(id:number ){
    let db = new Datastore({filename : 'ComerceDB'});
    db.loadDatabase(function() {
      db.remove({ _id: id }, {}, function (err:any, numRemoved:any) {

        this.idHiden = true
        console.log(this.idHiden) ;
      });
    });


}
}