APM模式，等待异步
APM模式，等待异步
提问于 2014-02-17 02:55:33
我需要关于如何使用APM模式的帮助，我现在正在阅读一些文章，但我恐怕没有太多的时间。我真正想要的是获取所有人员(来自db的数据)，然后获取照片并将其放在自动完成框代码中：
void listanomesautocomplete(object sender, ServicosLinkedIN.queryCompletedEventArgs e)
{
if (e.Result[0] != "")
{
for (int i = 0; i < e.Result.Count(); i = i + 3)
{
Pessoa pessoa = new Pessoa();
pessoa.Nome = e.Result[i];
pessoa.Id = Convert.ToInt32(e.Result[i + 1]);
if (e.Result[i + 2] == "")
pessoa.Imagem = new BitmapImage(new Uri("Assets/default_perfil.png", UriKind.Relative));
else
{
ServicosLinkedIN.ServicosClient buscaimg = new ServicosLinkedIN.ServicosClient();
buscaimg.dlFotoAsync(e.Result[i + 2]);
buscaimg.dlFotoCompleted += buscaimg_dlFotoCompleted;//when this completes it saves into a public bitmapimage and then i save it into pessoa.Imagem
//basicly, what happends, the listadlfotosasync only happends after this function
//what i want is to wait until it completes and have into the class novamsg
pessoa.Imagem = img;//saving the photo from dlFotoAsync
}
listaPessoas.Add(pessoa);
}
tbA_destinatario.ItemsSource = null;
tbA_destinatario.ItemsSource = listaPessoas;
BackgroundWorker listapessoas = new BackgroundWorker();
listapessoas.DoWork += listapessoas_DoWork;
listapessoas.RunWorkerAsync();
tb_lerdestmsg.Text = "";
}
else
{
tbA_destinatario.ItemsSource = null;
tb_lerdestmsg.Text = "Não encontrado";
}
}回答 2
Stack Overflow用户
回答已采纳
发布于 2014-02-17 03:40:24
这里有几件事要解决：
listanomesautocomplete事件处理程序应该是async。处理并报告在其中可能抛出的所有异常(通常，此规则适用于任何事件处理程序，但它对async事件处理程序更为重要，因为处理程序中的异步操作在触发事件的代码范围之外继续进行)。- 首先注册
dlFotoCompleted事件处理程序，然后调用dlFotoAsync。不要假设dlFotoAsync总是异步执行的。 - 考虑一下当另一个
listanomesautocomplete在上一次操作仍未完成时被触发的情况。这种情况可能是用户操作的结果。您可能希望取消并重新启动挂起的操作(如这)，或者在挂起的操作完成后立即排队执行一个新的操作(如这)。
回到问题上，您需要将EAP模式包装为Task，而不是APM。为此请使用TaskCompletionSource。代码的相关部分可能如下所示：
async void listanomesautocomplete(object sender, ServicosLinkedIN.queryCompletedEventArgs e)
{
if (e.Result[0] != "")
{
for (int i = 0; i < e.Result.Count(); i = i + 3)
{
Pessoa pessoa = new Pessoa();
pessoa.Nome = e.Result[i];
pessoa.Id = Convert.ToInt32(e.Result[i + 1]);
if (e.Result[i + 2] == "")
pessoa.Imagem = new BitmapImage(new Uri("Assets/default_perfil.png", UriKind.Relative));
else
{
// you probably want to create the service proxy
// outside the for loop
using (ServicosLinkedIN.ServicosClient buscaimg = new ServicosLinkedIN.ServicosClient())
{
FotoCompletedEventHandler handler = null;
var tcs = new TaskCompletionSource<Image>();
handler = (sHandler, eHandler) =>
{
try
{
// you can move the code from buscaimg_dlFotoCompleted here,
// rather than calling buscaimg_dlFotoCompleted
buscaimg_dlFotoCompleted(sHandler, eHandler);
tcs.TrySetResult(eHandler.Result);
}
catch (Exception ex)
{
tcs.TrySetException(ex);
}
};
try
{
buscaimg.dlFotoCompleted += handler;
buscaimg.dlFotoAsync(e.Result[i + 2]);
// saving the photo from dlFotoAsync
pessoa.Imagem = await tcs.Task;
}
finally
{
buscaimg.dlFotoCompleted -= handler;
}
}
}
listaPessoas.Add(pessoa);
}
tbA_destinatario.ItemsSource = null;
tbA_destinatario.ItemsSource = listaPessoas;
BackgroundWorker listapessoas = new BackgroundWorker();
listapessoas.DoWork += listapessoas_DoWork;
listapessoas.RunWorkerAsync();
tb_lerdestmsg.Text = "";
}
else
{
tbA_destinatario.ItemsSource = null;
tb_lerdestmsg.Text = "Não encontrado";
}
}Stack Overflow用户
发布于 2014-02-17 04:22:29
void listanomesautocomplete(object sender, ServicosLinkedIN.queryCompletedEventArgs e)
{
if (e.Result[0] != "")
{
List<Pessoa> listaPessoas = new List<Pessoa>();
for (int i = 0; i < e.Result.Count(); i = i + 3)
{
Pessoa pessoa = new Pessoa();
pessoa.Nome = e.Result[i];
pessoa.Id = Convert.ToInt32(e.Result[i + 1]);
if (e.Result[i + 2] == "")
pessoa.Imagem = new BitmapImage(new Uri("Assets/default_perfil.png", UriKind.Relative));
else
{
ServicosLinkedIN.ServicosClient buscaimg = new ServicosLinkedIN.ServicosClient();
buscaimg.dlFotoAsync(e.Result[i + 2]);
//THIS ACTUALLY WORKS!!!
//THE THREAD WAITS FOR IT!
buscaimg.dlFotoCompleted += (s, a) =>
{
pessoa.Imagem = ConvertToBitmapImage(a.Result);
};
}
listaPessoas.Add(pessoa);
}
if (tbA_destinatario.ItemsSource == null)
{
tbA_destinatario.ItemsSource = listaPessoas;
}
tb_lerdestmsg.Text = "";
}
else
{
tbA_destinatario.ItemsSource = null;
tb_lerdestmsg.Text = "Não encontrado";
}
}伙计，我一点也不生气，我很惊讶。诺塞雷肖，你的回答给了我一个主意，它确实奏效了！！非常感谢，伙计，我不能再感谢你了;)
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/21819937
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