如何获得传递给异步方法在回调参数 [英] How to get the parameters passed to the asynchronous method in the callback

问题描述

我需要被传输到AsyncSendRegistrationMethod在CallbackMethodSendRegistration的标签。

 私人委托ResponceFromServer AsyncSendRegistrationDelegate（RegistrationToUser registrationToUser，标签标签）; 
私人ResponceFromServer AsyncSendRegistrationMethod（RegistrationToUser registrationToUser，标签标签）
 {
的setText（标签，registrationToUser.Name +注册...）; 
 
 
返回Requests.DataBase.Authorization.Registration（
 registrationToUser.Name，
 registrationToUser.IdRoleUser，
 registrationToUser.IdGroup）; 
} 
私人无效CallbackMethodSendRegistration（IAsyncResult的AR）
 {
 VAR sendRegistrationDelegate =（AsyncSendRegistrationDelegate）ar.AsyncState; 
 
 VAR responceFromServer =（ResponceFromServer）sendRegistrationDelegate.EndInvoke（AR）; 
如果（responceFromServer.IsError）
 {
 //这里需要label.Text 
} 
，否则
 {
 
} 
} 
  

解决方案

要得到一个参考的一种方式传递给sendRegistrationDelegate标签是由具有回调是一个lambda。在调用点，这将是这样的：

  VAR registrationToUser = ...; 
变种标签= ...; 
 
 sendRegistrationDelegate.BeginInvoke（registrationToUser，标签，AR => 
 {
 VAR responceFromServer = sendRegistrationDelegate.EndInvoke（AR）; 
如果（responceFromServer.IsError）
 {
 label.Text =; 
} 
，否则
 {
 
} 
}，NULL）; 
  

I need a Label that is transmitted to the AsyncSendRegistrationMethod in CallbackMethodSendRegistration.

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
    {

    }
}

解决方案

One way to get a reference to the label passed to sendRegistrationDelegate is by having the callback be a lambda. At the call site this would look like this:

    var registrationToUser = ...;
    var label = ...;

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

        }
    }, null);

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