[英]Cancel Async Task from a button
What I need to do is be able to cancel a task that is running async. 我需要做的是能够取消运行异步的任务。
I have been searching and cannot seem to wrap my head around it. 我一直在寻找,似乎无法绕过它。 I just cant seem to discern how it would be implemented into my current setup. 我似乎无法辨别它将如何实现到我当前的设置中。
Here is my code that fires my task off. 这是我的代码,它解雇了我的任务。 Any help on where or how to implement a cancellation token would be greatly appreciated. 任何有关在何处或如何实施取消令牌的帮助将不胜感激。
private async void startThread()
{
//do ui stuff before starting
ProgressLabel.Text = String.Format("0 / {0} Runs Completed", index.Count());
ProgressBar.Maximum = index.Count();
await ExecuteProcesses();
//sort list of output lines
outputList = outputList.OrderBy(o => o.RunNumber).ToList();
foreach (Output o in outputList)
{
string outStr = o.RunNumber + "," + o.Index;
foreach (double oV in o.Values)
{
outStr += String.Format(",{0}", oV);
}
outputStrings.Add(outStr);
}
string[] csvOut = outputStrings.ToArray();
File.WriteAllLines(settings.OutputFile, csvOut);
//do ui stuff after completing.
ProgressLabel.Text = index.Count() + " runs completed. Output written to file test.csv";
}
private async Task ExecuteProcesses()
{
await Task.Factory.StartNew(() =>
{
int myCount = 0;
int maxRuns = index.Count();
List<string> myStrings = index;
Parallel.ForEach(myStrings,
new ParallelOptions()
{
MaxDegreeOfParallelism = settings.ConcurrentRuns
}, (s) =>
{
//This line gives us our run count.
int myIndex = myStrings.IndexOf(s) + 1;
string newInputFile = Path.Combine(settings.ProjectPath + "files/", Path.GetFileNameWithoutExtension(settings.InputFile) + "." + s + ".inp");
string newRptFile = Path.Combine(settings.ProjectPath + "files/", Path.GetFileNameWithoutExtension(settings.InputFile) + "." + s + ".rpt");
try
{
//load in contents of input file
string[] allLines = File.ReadAllLines(Path.Combine(settings.ProjectPath, settings.InputFile));
string[] indexSplit = s.Split('.');
//change parameters here
int count = 0;
foreach (OptiFile oF in Files)
{
int i = Int32.Parse(indexSplit[count]);
foreach (OptiParam oP in oF.Parameters)
{
string line = allLines[oP.LineNum - 1];
if (oP.DecimalPts == 0)
{
string sExpression = oP.Value;
sExpression = sExpression.Replace("%i", i.ToString());
EqCompiler oCompiler = new EqCompiler(sExpression, true);
oCompiler.Compile();
int iValue = (int)oCompiler.Calculate();
allLines[oP.LineNum - 1] = line.Substring(0, oP.ColumnNum - 1) + iValue.ToString() + line.Substring(oP.ColumnNum + oP.Length);
}
else
{
string sExpression = oP.Value;
sExpression = sExpression.Replace("%i", i.ToString());
EqCompiler oCompiler = new EqCompiler(sExpression, true);
oCompiler.Compile();
double dValue = oCompiler.Calculate();
dValue = Math.Round(dValue, oP.DecimalPts);
allLines[oP.LineNum - 1] = line.Substring(0, oP.ColumnNum - 1) + dValue.ToString() + line.Substring(oP.ColumnNum + oP.Length);
}
}
count++;
}
//write new input file here
File.WriteAllLines(newInputFile, allLines);
}
catch (IOException ex)
{
MessageBox.Show(ex.ToString());
}
var process = new Process();
process.StartInfo = new ProcessStartInfo("swmm5.exe", newInputFile + " " + newRptFile);
process.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;
process.Start();
process.WaitForExit();
Output output = new Output();
output.RunNumber = myIndex;
output.Index = s;
output.Values = new List<double>();
foreach(OutputValue oV in OutputValues) {
output.Values.Add(oV.getValue(newRptFile));
}
outputList.Add(output);
//get rid of files after run
File.Delete(newInputFile);
File.Delete(newRptFile);
myCount++;
ProgressBar.BeginInvoke(
new Action(() =>
{
ProgressBar.Value = myCount;
}
));
ProgressLabel.BeginInvoke(
new Action(() =>
{
ProgressLabel.Text = String.Format("{0} / {1} Runs Completed", myCount, maxRuns);
}
));
});
});
}
The best way to support cancellation is to pass a CancellationToken
to the async
method. 支持取消的最佳方法是将CancellationToken
传递给async
方法。 The button press can then be tied to cancelling the token 然后可以按下按钮以取消令牌
class TheClass
{
CancellationTokenSource m_source;
void StartThread() {
m_source = new CancellationTokenSource;
StartThread(m_source.Token);
}
private async void StartThread(CancellationToken token) {
...
}
private void OnCancelClicked(object sender, EventArgs e) {
m_source.Cancel();
}
}
This isn't quite enough though. 但这还不够。 Both the startThread
and StartProcess
methods will need to be updated to cooperatively cancel the task once the CancellationToken
registers as cancelled 一旦CancellationToken
注册为取消,则需要更新startThread
和StartProcess
方法以协同取消任务
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