/// <summary>
/// Performs an asynchronous task in foreground (blocking the host form's user input) and reports its progress.
/// </summary>
/// <typeparam name="T">The task's result type</typeparam>
/// <param name="host">The host form</param>
/// <param name="taskContext">The task to perform</param>
/// <param name="onSuccess">What to do if the operation succeceeds; the parameter is the task's result</param>
/// <param name="onError">What to do if the operation fails; the parameter is the cause of the failure</param>
public static void PerformForegroundTask <T>(Form host, IReportingTask <T> taskContext, Action <T> onSuccess, Action <Exception> onError)
{
// Disable the host form (like ShowDialog would do)
host.Enabled = false;
var reporter = new ProgressReporter(taskContext);
reporter.Show(host);
// When the task completes,
taskContext.Task.ContinueWith(delegate
{
// Determine if there was an error
bool success = false;
bool canceled = taskContext.Task.IsCanceled;
Exception error = null;
if (!taskContext.Task.IsCanceled)
{
error = taskContext.Task.Exception;
// It really sucks to have an aggregate exception with a single inner...
while (error != null && error is AggregateException && (error as AggregateException).InnerExceptions.Count == 1)
{
error = error.InnerException;
}
// Target invocation exceptions are also meaningless wrappers
while (error != null && error is TargetInvocationException)
{
error = error.InnerException;
}
success = error == null;
}
// Bring back the host context (in its own thread)
bool enteredOnce = false;
Action bringBackHostContext = () =>
{
if (!enteredOnce)
{
enteredOnce = true;
reporter.Close();
reporter = null;
host.Enabled = true;
host.Focus();
// Execute the provided actions
if (success)
{
var result = taskContext.Task.Result;
taskContext.Dispose();
onSuccess(result);
}
else if (!canceled)
{
taskContext.Dispose();
onError(error);
}
}
};
// Try as many times as required, but only allow 1 execution of the action
IAsyncResult ar = host.BeginInvoke(bringBackHostContext);
while (!ar.AsyncWaitHandle.WaitOne(100, false) && !enteredOnce)
{
ar = host.BeginInvoke(bringBackHostContext);
}
});
}
