binding two selects angular - angularjs

Question

I have two selects
The first one is for regions
and the second one for cities
The first one is filled with regions
Now i have a methode that brings cities by the id of the region .
I dont know how to get the idregion and put it into the params function
This is my first select
<div class="form-group">
<label for="">Region</label>
<select class="form-control"
[(ngModel)]="region" name="Region">
<option></option>
<option *ngFor="let region of
objectKeys(dropDownList2)|keys"
[value]="dropDownList2[region].idRegion">
{{dropDownList2[region].nomRegion}}
</option>
</select>
</div>
My services :
getville() {
return this.http.get(this.urltest + 'Villes');
}
getRegion() {
return this.http.get(this.urltest + 'Regions');
}
GetRegionVille(idRegion) {
return this.http.get(this.urltest + 'Villes/GetRegionVille/' + idRegion);
}
My component.ts :
getidregion() {
this.res.getRegion().subscribe(R => {
this.dropDownList2 = R as any;
});
}
getregionville() {
this.res.GetRegionVille(****i don t know how to get the idregion**** )
.subscribe(response => {
this.dropDownList = response as any;
});
}
this is my function
// GET: api/Villes
[HttpGet("GetRegionVille/{id}")]
public async Task<IActionResult> GetRegionVille([FromRoute] int id)
{
var req = from v in _context.Villes
join r in _context.Regions
on v.IdRegion equals r.IdRegion
where r.IdRegion == id
select new {v.NomVille };
return Ok(req);
}
My select of the cities :
<div class="form-group">
<label for="">Ville</label>
<select class="form-control" name="Ville"
[(ngModel)]="ville">
<option></option>
<option *ngFor="let ville of objectKeys(dropDownList) |
keys"
[value]="dropDownList[ville].idVille">
{{dropDownList[ville].nomVille}}
</option>
</select>

Answer 1

The selected value will be in region variable as you state [(ngModel)]="region" and you can use (ngModelChange)="onChange($event)" to get an event when value changes
I am not sure if using two way data binding with (ngModelChange) is efficient, so please see this answer How can I get new selection in "select" in Angular 2?