System.AccessViolationException发生从System.Net.Http C＃

Question

我有以下代码：

using (var ct = new Google.Apis.SearchConsole.v1.SearchConsoleService(new BaseClientService.Initializer
 {
    ApiKey = ConfigurationManager.AppSettings["googleSearchApiKey"],
    ApplicationName = "my info"
 }))
 {

    html = ct.HttpClient.GetStringAsync("https://www.google.com/search?q=" + WebUtility.UrlEncode(gameName) + "+origin+pc+game").Result;
 }

 HtmlDocument doc = new HtmlDocument();
 doc.LoadHtml(html);

 var glist = doc.DocumentNode.GetById("search")?.GetByClass("g");
 if (glist != null)
 {
    var off = glist.First();
    var a = off.GetByTag("a").FirstOrDefault();

    if (a != null)
    {
       var url = a.GetAttributeValue("href", "");

       if (!string.IsNullOrWhiteSpace(url))
       {
          url = WebUtility.UrlDecode(url);
          url = url.Substring(url.IndexOf("?q=") + 3);
          url = url.Substring(0, url.IndexOf('&'));

          gameUrl = url;
          return stuff;
       }
    }
 }

到达ct.HttpClient.GetStringAsync时，我得到了漂亮的错误页面：

  

应用程序：MyApp.exe       框架版本：v4.0.30319       说明：由于未处理的异常，进程已终止。       异常信息：System.AccessViolationException          在System.Net.Http.HttpClient.SendAsync（System.Net.Http.HttpRequestMessage，System.Net.Http.HttpCompletionOption，System.Threading.CancellationToken）          在System.Net.Http.HttpClient.GetAsync（System.Uri，System.Net.Http.HttpCompletionOption，System.Threading.CancellationToken）

为什么？