我尝试过（但失败了）从WPF应用程序进行异步Web服务调用。
BackgroundWorker当您按我的GUI上的“发送”按钮时，我在我的代码中实现了应该执行的工作。它有时会执行预期的操作，但最终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只是一个有数字的盒子。它将确定您一次发送到Web服务的请求数量。
progressBar 是您期望的：进度条。
worker.RunWorkerAsync()是我调用该DoWork方法的地方。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，这是我理所当然的地方。我希望应用程序发送与用户指定数量一样多的请求。因此，如果我写了10封，我将发送10封请求。该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;
}
我将如何使该DoWork方法实际发送请求异步？
就UI线程而言，代码原样是异步的；您在问它的并发性是什么。任何类型的复杂I / O工作都最好使用async/来完成await，因此我将淘汰您的后台工作人员，而直接使用async。
首先，按钮处理程序将处理其自己的启用/禁用和执行主要下载：
private async void btnSend_Click(object sender, RoutedEventArgs e)
{
var quantity = int.Parse(boxQuantity.Text);
btnSend.Enabled = false;
await DownloadAsync(quantity);
btnSend.Enabled = true;
}
主要下载将创建一个速率限制SemaphoreSlim（一种用于限制并发异步操作的通用类型），并等待所有单个下载完成：
private async Task DownloadAsync(int quantity)
{
var semaphore = new SemaphoreSlim(quantity);
var tasks = GetData().Select(dto => DownloadAsync(dto, semaphore));
await Task.WhenAll(tasks);
}
单独的下载将各自先限制自己的速率，然后再进行实际的下载：
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，我建议使用用于该模式的类型（IProgress<T>/ Progress<T>）。首先，您决定要在进度报告中使用哪些数据；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，progressBar.Maximum = double.Parse(sQuantity);原始代码中的错误；您应该将其设置为下载总数）。
然后IProgress<string>公正传下来：
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);
}
而且，当您有进度报告时，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();
}
}
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