如何在回调中获取传递给异步方法的参数答案

【问题标题】：How to get the parameters passed to the asynchronous method in the callback如何在回调中获取传递给异步方法的参数
【发布时间】：2011-09-27 02:49:06
【问题描述】：

我需要一个Label，它被传送到CallbackMethodSendRegistration中的AsyncSendRegistrationMethod。

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
    {

    }
}

【问题讨论】：

标签： c# callback c#-2.0 asynccallback

【解决方案1】：

获取对传递给 sendRegistrationDelegate 的标签的引用的一种方法是将回调设为 lambda。在呼叫站点，这将如下所示：

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

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

        }
    }, null);

【讨论】：