Webservice Call上的Xamarin ObjectDisposedException

Question

在升级到最新xamarin.android后调用webservices时，我收到了很多 objectdisposed 异常。有什么想法吗？

Error: System.ObjectDisposedException: Cannot access a disposed object.
    Object name: 'System.Net.Sockets.NetworkStream'.
    at System.Net.HttpWebRequest.EndGetResponse (IAsyncResult asyncResult)
    at System.Net.HttpWebRequest.GetResponse
    at System.Web.Services.Protocols.WebClientProtocol.GetWebResponse(System.Net.WebRequest request)
    at System.Web.Services.Protocols.HttpWebClientProtocol.GetWebResponse (System.Net.WebRequest request)
    at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke (System.String method_name, System.Object[] parameters)