create a simple event handler for the click event of the button.
async void Start_Button_Click(object sender, RoutedEventArgs e)
{
//start the first long running task in parallel
await LongRunningTask(Progress00_ProgresBar);
//print something to the textbox
TextBoxOne.Text = "First Progress Bar Complete";
//show a message to the user
await new MessageDialog("Good Times").ShowAsync();
//start the second long running task in parallel
await LongRunningTask(Progress01_ProgresBar);
//print something to the second textbox
TextBoxTwo.Text = "Second Progress Bar Complete";
}
public void LongRunningTask(ProgressBar pb)
{
for (var i = 0; i <= 100; i+=20)
{
Task.Delay(1000).Wait();
pb.Value = i;
}
}
Now that worked great, that is unless you clicked the start button again before the whole process finished, kinda bunk what we need to do is be able to cancel our tasks if the start button is clicked. to do this we need to add a CancellationTokenSource, let's go ahead and create a property right on the page.
with that done let's modify our start event handler
async void Start_Button_Click(object sender, RoutedEventArgs e)
Next we modify our long running function to accept the cancellation token and use it to terminate the task if it's signaled to cancel.
we pass in our token and then if we signal it, our long running task will stop and throw an cancellation request winch will halt our start event handler.
Now that worked great, that is unless you clicked the start button again before the whole process finished, kinda bunk what we need to do is be able to cancel our tasks if the start button is clicked. to do this we need to add a CancellationTokenSource, let's go ahead and create a property right on the page.
public sealed partial class MainPage : Page
{
CancellationTokenSource cts { get; set; }
//Our Code ...
}
async void Start_Button_Click(object sender, RoutedEventArgs e)
{
//Check if cancellation token source is instantiated
if (this.cts != null) {
//if it is, that means we're running and cancel
cts.Cancel(true);
}
else
{
cts = new CancellationTokenSource();
try
{
//start
the first long running task in parallel
await LongRunningTask(Progress00_ProgresBar, cts.Token);
//print
something to the textbox
TextBoxOne.Text = "First Progress Bar Complete";
//show a
message to the user
await new MessageDialog("Good Times").ShowAsync();
//start
the second long running task in parallel
await LongRunningTask(Progress01_ProgresBar, cts.Token);
//print
something to the second textbox
TextBoxTwo.Text = "Second Progress Bar Complete";
}
//catch cancellation exception from LongRunning function
catch (OperationCanceledException ocex)
{
new MessageDialog("Operation
Canceled, click start again").ShowAsync();
}
finally
{
//canceled or finished set the cancellation token source to null
this.cts = null;
}
}
}
async Task LongRunningTask(ProgressBar pb, CancellationToken token)
{
for (var i = 0; i <= 100; i += 20)
{
await Task.Delay(1000);
//if
cancel signal sent, break the loop
if (token.IsCancellationRequested)
break;
await this.Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () => pb.Value = i);
}
//throw
cancelation exception
token.ThrowIfCancellationRequested();
}
we pass in our token and then if we signal it, our long running task will stop and throw an cancellation request winch will halt our start event handler.
