如何获取在回调中传递给异步方法的参数

我需要一个传递给CallbackMethodSendRegistration中的AsyncSendRegistrationMethod的Label。

private delegate ResponceFromServer AsyncSendRegistrationDelegate(RegistrationToUser registrationToUser, Label label); private ResponceFromServer AsyncSendRegistrationMethod(RegistrationToUser registrationToUser, Label label) { SetText(label, registrationToUser.Name + " registration..."); return Requests.DataBase.Authorization.Registration( registrationToUser.Name, registrationToUser.IdRoleUser, registrationToUser.IdGroup); } private void CallbackMethodSendRegistration(IAsyncResult ar) { var sendRegistrationDelegate = (AsyncSendRegistrationDelegate)ar.AsyncState; var responceFromServer = (ResponceFromServer)sendRegistrationDelegate.EndInvoke(ar); if(responceFromServer.IsError) { //here need label.Text } else { } } 

Answer 1

获取对传递给sendRegistrationDelegate的标签的引用的一种方法是使回调为lambda。 在呼叫站点，这将是这样的：

  var registrationToUser = ...; var label = ...; sendRegistrationDelegate.BeginInvoke(registrationToUser, label, ar => { var responceFromServer = sendRegistrationDelegate.EndInvoke(ar); if (responceFromServer.IsError) { label.Text = ""; } else { } }, null);