how to call google acknowledge api from wcf service? - asp.net

Question

i need to add a call to google acknowledge endpoint into existing dotnet web service app.
this is the refence page https://developers.google.com/android-publisher/api-ref/rest/v3/purchases.products/acknowledge
i never worked on this app before, and i can not ask who developed it, He went away.
in the web.config are stored PlayStore ClientId and ClientSecret.
this is existing and working call to check a subscription:
internal PlayStoreSubscriptionPurchaseStatus verifySubscription(string packageName, string subscriptionId, string token, ref long timeMills)
{
Stopwatch watcher = new Stopwatch();
string accessToken = this.generateNewAccessToken(ref timeMills);
string verifySubscriptionAddress = _playStoreApisAddress + packageName + "/purchases/subscriptions/" + subscriptionId + "/tokens/" + token + "?access_token=" + accessToken;
PlayStoreSubscriptionPurchaseStatus playStoreResponse = null;
try
{
HttpWebRequest verifyRequest = WebRequest.Create(verifySubscriptionAddress) as HttpWebRequest;
verifyRequest.Method = "GET";
verifyRequest.ContentType = "application/json; charset=utf-8";
verifyRequest.Accept = "application/json; charset=utf-8";
watcher.Start();
using (HttpWebResponse verifyResponse = verifyRequest.GetResponse() as HttpWebResponse)
{
watcher.Stop();
Stream responseStream = verifyResponse.GetResponseStream();
StreamReader streamReader = new StreamReader(responseStream);
string responseAsString = streamReader.ReadToEnd();
JavaScriptSerializer jss = new JavaScriptSerializer();
if (verifyResponse.StatusCode == HttpStatusCode.OK)
playStoreResponse = jss.Deserialize<PlayStoreSubscriptionPurchaseStatus>(responseAsString);
else
{
playStoreResponse = new PlayStoreSubscriptionPurchaseStatus() { Success = false, ErrorMessage = responseAsString };
}
}
}
catch (WebException webEx)
{
using (StreamReader streamReader = new StreamReader(webEx.Response.GetResponseStream()))
{
string webExResponse = streamReader.ReadToEnd();
throw new Exception("Errore nella verifica subscription google play.\nErrore restituito dalle api google play:\n" + webExResponse);
}
}
finally
{
if (watcher.IsRunning)
watcher.Stop();
timeMills += watcher.ElapsedMilliseconds;
}
return playStoreResponse;
}
this code generates access_token:
private string generateNewAccessToken(ref long timeMills)
{
Stopwatch watcher = new Stopwatch();
string newAccessToken = string.Empty;
string postDta = string.Format("grant_type={0}&client_id={1}&client_secret={2}&refresh_token={3}",
"refresh_token", Uri.EscapeDataString(_clientId), Uri.EscapeDataString(_clientSecret), Uri.EscapeDataString(_refreshToken));
try
{
HttpWebRequest refreshAccessTokenRequest = WebRequest.Create(_refreshTokenAddress) as HttpWebRequest;
refreshAccessTokenRequest.Method = "POST";
refreshAccessTokenRequest.ContentType = "application/x-www-form-urlencoded";
//refreshAccessTokenRequest.ContentLength = new UTF8Encoding().GetBytes(postDta).Length;
refreshAccessTokenRequest.Accept = "application/json; charset=utf-8";
Stream refreshTokenRequestStream = refreshAccessTokenRequest.GetRequestStream();
StreamWriter streamWriter = new StreamWriter(refreshTokenRequestStream);
streamWriter.Write(postDta);
streamWriter.Close();
watcher.Start();
using (HttpWebResponse refreshAccessTokenResponse = refreshAccessTokenRequest.GetResponse() as HttpWebResponse)
{
watcher.Stop();
Stream responseStream = refreshAccessTokenResponse.GetResponseStream();
StreamReader streamReader = new StreamReader(responseStream);
string responseAsString = streamReader.ReadToEnd();
JavaScriptSerializer jss = new JavaScriptSerializer();
RenewAccessTokenResponse renewAccessTokenResponse = jss.Deserialize<RenewAccessTokenResponse>(responseAsString);
newAccessToken = renewAccessTokenResponse.access_token;
}
}
catch (WebException webEx)
{
using (StreamReader streamReader = new StreamReader(webEx.Response.GetResponseStream()))
{
string webExResponse = streamReader.ReadToEnd();
throw new Exception(webExResponse);
}
}
finally
{
if (watcher.IsRunning)
watcher.Stop();
timeMills += watcher.ElapsedMilliseconds;
}
return newAccessToken;
}
what i want to know is if i can, using only httpwebrequest, make a call to acknlowelage api,
access token generate from generateNewAccessToken is good for this api?
if yes where do i have to store it? acknlowelage is POST while all existing calls in the project are GET. do i have store the access code in body or into some header?
there is somewhere a working sample?
thanks.