我已经尝试(但失败了)从 WPF 应用程序进行异步 Web 服务调用。
我在我的代码中实现了一个 BackgroundWorker，当您在我的 GUI 上按下“发送”按钮时，它应该可以完成这项工作。它做了它应该做的事，有时，但最终它实际上并没有异步运行。
当您在我的 GUI 中按下按钮时，将触发以下代码:
private void btnSend_Click(object sender, RoutedEventArgs e)
{
sQuantity = boxQuantity.Text;
progressBar.Maximum = double.Parse(sQuantity);
worker.RunWorkerAsync();
}
sQuantity 只是一个带有数字的框。它将确定您一次向网络服务发送了多少请求。
progressBar 是您所期望的:进度条。
worker.RunWorkerAsync() 是我调用 DoWork 方法的地方。它看起来像这样:
void worker_DoWork(object sender, DoWorkEventArgs e)
{
EnableButton(false);
List<LoanRequestNoCreditScoreDTO> dtoList = GetData();
foreach (LoanRequestNoCreditScoreDTO dto in dtoList)
{
using (LoanBrokerWS.LoanBrokerWSClient client = new LoanBrokerWS.LoanBrokerWSClient())
{
try
{
Task<LoanQuoteDTO> lq = RequestQuote(dto, client);
LoanQuoteDTO response = lq.Result;
lq.Dispose();
String responseMsg = response.SSN + "\n" + response.interestRate + "\n" + response.BankName + "\n------\n";
AppendText(responseMsg);
worker_ProgressChanged();
}
catch (Exception ex)
{
AppendText(ex.Message + "\n" + ex.InnerException.Message + "\n");
worker_ProgressChanged();
}
}
}
EnableButton(true);
}
最终，这当然是我搞砸的地方。我希望应用程序发送与用户指定的一样多的请求。所以如果我写了 10 个数量，我会发送 10 个请求。 RequestQuote() 方法调用以下代码:
private async Task<LoanQuoteDTO> RequestQuote(LoanRequestNoCreditScoreDTO dto, LoanBrokerWS.LoanBrokerWSClient client)
{
LoanQuoteDTO response = await client.GetLoanQuoteAsync(dto.SSN, dto.LoanAmount, dto.LoanDuration);
return response;
}
我如何使 DoWork 方法实际发送异步请求？
请您参考如下方法:
相对于 UI 线程，代码是异步的；你问的是什么并发性。任何类型的复杂 I/O 工作最好用 async 完成。/await ，所以我要扔掉你的后台工作人员，直接使用 async .
首先，按钮处理程序将处理它自己的启用/禁用和执行主下载:
private async void btnSend_Click(object sender, RoutedEventArgs e)
{
var quantity = int.Parse(boxQuantity.Text);
btnSend.Enabled = false;
await DownloadAsync(quantity);
btnSend.Enabled = true;
}
主下载会创建限速SemaphoreSlim (一种用于限制并发异步操作的常见类型)，并等待所有单独的下载完成:
private async Task DownloadAsync(int quantity)
{
var semaphore = new SemaphoreSlim(quantity);
var tasks = GetData().Select(dto => DownloadAsync(dto, semaphore));
await Task.WhenAll(tasks);
}
每个单独的下载都会首先限制自己的速率，然后再进行实际下载:
private async Task DownloadAsync(LoanRequestNoCreditScoreDTO dto, SemaphoreSlim semaphore)
{
await semaphore.WaitAsync();
try
{
using (LoanBrokerWS.LoanBrokerWSClient client = new LoanBrokerWS.LoanBrokerWSClient())
{
var response = await RequestQuoteAsync(dto, client);
}
}
finally
{
semaphore.Release();
}
}
对于进度报告，我建议使用适用于该模式的类型 ( IProgress<T>/Progress<T> )。首先，您决定进度报告中需要哪些数据；在这种情况下，它可能只是一个字符串。然后，您创建进度处理程序:
private async void btnSend_Click(object sender, RoutedEventArgs e)
{
var quantity = int.Parse(boxQuantity.Text);
var progress = new Progress<string>(update =>
{
AppendText(update);
progressBar.Value = progressBar.Value + 1;
});
progressBar.Maximum = ...; // not "quantity"
btnSend.Enabled = false;
await DownloadAsync(quantity, progress);
btnSend.Enabled = true;
}
(请注意，原始代码中的progressBar.Maximum = double.Parse(sQuantity); 是错误的；您应将其设置为总 下载次数)。
然后 IProgress<string>刚刚被传下来:
private async Task DownloadAsync(int quantity, IProgress<string> progress)
{
var semaphore = new SemaphoreSlim(quantity);
var tasks = GetData().Select(dto => DownloadAsync(dto, semaphore, progress));
await Task.WhenAll(tasks);
}
当您有进展要报告时，您可以使用该实例:
private async Task DownloadAsync(LoanRequestNoCreditScoreDTO dto, SemaphoreSlim semaphore, IProgress<string> progress)
{
await semaphore.WaitAsync();
try
{
using (LoanBrokerWS.LoanBrokerWSClient client = new LoanBrokerWS.LoanBrokerWSClient())
{
var response = await RequestQuoteAsync(dto, client);
progress.Report(response.SSN + "\n" + response.interestRate + "\n" + response.BankName + "\n------\n");
}
}
catch (Exception ex)
{
progress.Report(ex.Message + "\n" + ex.InnerException.Message + "\n");
}
finally
{
semaphore.Release();
}
}
