c# - async と await を使用して HTTP GET リクエストを実行する方法

Question

URL をパラメーターとして取り、そこから GET 応答を返す関数を作成しようとしていますが、WebResponse responseObject intialization行にエラーが表示されるだけです

例外はAn exception of type 'System.Net.ProtocolViolationException' occurred in mscorlib.ni.dll but was not handled in user code

public static async Task<string> get(string url)
{
    var request = WebRequest.Create(new Uri(url)) as HttpWebRequest;
    request.Method = "GET";
    request.ContentType = "application/json";
    WebResponse responseObject = await Task<WebResponse>.Factory.FromAsync(request.BeginGetResponse, request.EndGetResponse, request);
    var responseStream = responseObject.GetResponseStream();
    var sr = new StreamReader(responseStream);
    string received = await sr.ReadToEndAsync();

    return received;
}

Answer 1

代わりに、次のように HttpClient で試してください。

    public async Task<List<MyClass>> GetMyClassAsync(
    CancellationToken cancelToken = default(CancellationToken))
    {
        using (HttpClient httpClient = new HttpClient())
        {
            var uri = Util.getServiceUri("myservice");
            var response = await httpClient.GetAsync(uri, cancelToken);
            return (await response.Content.ReadAsAsync<List<MyClass>>());
        }
    }