如何在回调中获取传递给异步方法的参数

问题描述

我需要在 CallbackMethodSendRegistration 中传输到 AsyncSendRegistrationMethod 的标签.

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
    {

    }
}

推荐答案

获取对传递给 sendRegistrationDelegate 的标签的引用的一种方法是让回调为 lambda.在呼叫站点，这看起来像这样:

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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