[英]How to wait until all tasks finished without blocking UI thread?
在下面的代码中,我在处理任务之前禁用按钮,并希望在所有任务完成后启用它。
List<Task> tasks = new List<Task>();
buttonUpdateImage.Enabled = false; // disable button
foreach (OLVListItem item in cellsListView.CheckedItems)
{
Cell c = (Cell)(item.RowObject);
var task = Task.Factory.StartNew(() =>
{
Process p = new Process();
...
p.Start();
p.WaitForExit();
});
task.ContinueWith(t => c.Status = 0);
tasks.Add(task);
}
Task.WaitAll(tasks.ToArray());
// enable button here
WaitAll
正在阻止UI线程。 我怎么能等到所有任务完成然后启用按钮?
首先,我将安装Microsoft.Bcl.Async
,它将支持在.NET 4.0中使用async-await
。
现在,使用这个问题的答案,您可以异步注册进程退出,而无需使用Task.Factory.StartNew
:
public static class ProcessExtensions
{
public static Task RunProcessAsync(this Process process, string fileName)
{
if (process == null)
throw new ArgumentNullException(nameof(process));
var tcs = new TaskCompletionSource<bool>();
process.StartInfo = new ProcessStartInfo
{
FileName = fileName
};
process.EnableRaisingEvents = true
process.Exited += (sender, args) =>
{
tcs.SetResult(true);
process.Dispose();
};
process.Start();
return tcs.Task;
}
}
现在,你可以这样做:
buttonUpdateImage.Enabled = false; // disable button
var tasks = cellsListView.CheckedItems.Cast<OLVListItem>()
.Select(async item =>
{
Cell cell = (Cell)item.RowObject;
var process = new Process();
await process.RunProcessAsync("path");
cell.Status = 0;
});
await Task.WhenAll(tasks);
buttonUpdateImage.Enabled = true;
List<Task> tasks = new List<Task>();
buttonUpdateImage.Enabled = false; // disable button
foreach (OLVListItem item in cellsListView.CheckedItems)
{
Cell c = (Cell)(item.RowObject);
var task = Task.Factory.StartNew(() =>
{
Process p = new Process();
...
p.Start();
p.WaitForExit();
}).ContinueWith(t => c.Status = 0); // this modification is very important, Please note it, this will fix a problem
tasks.Add(task);
}
// your code has been modified to just make the task object
// is the continued task instead of the task is the original task
// Task.WaitAll and add this instead of it.
Task.Factory.ContinueWhenAll(tasks.ToArray(), ac => buttonUpdateImage.Enabled = true;);
其他方式 .....
// Note this object.
Barrier b = new Barrier(cellsListView.CheckedItems.Count, () => {
// enable the button here
buttonUpdateImage.Enabled = true;
});
buttonUpdateImage.Enabled = false; // disable button
foreach (OLVListItem item in cellsListView.CheckedItems)
{
Cell c = (Cell)(item.RowObject);
var task = Task.Factory.StartNew(() =>
{
Process p = new Process();
...
p.Start();
p.WaitForExit();
}).ContinueWith(t => {
c.Status = 0;
b.SignalAndWait();
});
}
第一种方式比第二种方式更好,我建议你使用第一种方式。
您可以创建一个新任务来运行WaitAll
方法,就像
Task.Factory.StartNew(() =>
{
Task.WaitAll(tasks.ToArray());
Action act = () =>
{
this.button1.Enabled = true;
};
this.button1.Invoke(act);
});
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