MainWindow main = new MainWindow();

var client_id = 123456;
var client_secret = "qwerty";
var AudioBotVk = new HttpClient();
//WebProxy webProxy = new WebProxy(main.ProxyBox.ToString(), true);

HttpWebRequest request = (HttpWebRequest)WebRequest.Create("https://oauth.vk.com/token?scope=nohttps%2Call&client_id="
+ client_id + "&client_secret=" + client_secret + "&2fa_supported=1&lang=ru&grant_type=password&username="
+ main.LoginBox.Text.ToString() + "&password=" + main.PasswordBox.ToString() +
"&libverify_support=1");

request.Method = "GET";
request.Host = "oauth.vk.com";
request.UserAgent = "Foo/bar (param1; param2; param3; param4; ru)";
request.ContentType = "application/x-www-form-urlencoded";


HttpWebResponse responsevk = (HttpWebResponse)request.GetResponse();