/// <summary>
/// Resumes the execution of the specified recurring operation
/// if currently in Paused state. Resuming a cancelled operation
/// throws an exception.
/// </summary>
/// <param name="recurringOperation"></param>
/// <param name="interval"></param>
/// <param name="action"></param>
/// <param name="startImmediately"></param>
public void ResumeRecurring(RecurringOperation recurringOperation, bool startImmediately = false)
{
// If operation is not initialized
if (recurringOperation == null || string.IsNullOrWhiteSpace(recurringOperation.GetName()))
{
throw new InvalidOperationException(Constants.UninitializedOperationException);
}
// If cancelled
if (recurringOperation.Status == RecurringOperationStatus.Cancelled)
{
var exception = new InvalidOperationException(Constants.CancelledOperationException);
recurringOperation.Exception = exception;
throw exception;
}
// Search for the operation reference
var operation = recurringOperations.Find(op => op.Name.Equals(recurringOperation.GetName()));
// If an operation was found
if (operation != null)
{
// Set operation status
recurringOperation.Status = RecurringOperationStatus.Idle;
recurringOperation.IsIdle = true;
recurringOperation.IsRecurring = true;
recurringOperation.IsNotRecurring = false;
recurringOperation.IsPaused = false;
recurringOperation.IsExecuting = false;
// Resume the operation
operation.Timer.Change(
startImmediately ? TimeSpan.Zero : operation.Interval, operation.Interval);
}
}
/// <summary>
/// Cancels the specified recurring operation.
/// Cancelled operations cannot be resumed, they must be restarted
/// with a call to StartRecurring().
/// </summary>
/// <param name="backgroundOperation"></param>
public void CancelRecurring(RecurringOperation backgroundOperation)
{
// Find a reference to an internal operation
var internalOperation =
recurringOperations.Find(
operation => operation.Name.Equals(backgroundOperation.GetName()));
// If found
if (internalOperation != null)
{
// Dispose the timer and the operation object
internalOperation.Timer.Dispose();
recurringOperations.Remove(internalOperation);
// Set the status flags of the public facing background operation object
backgroundOperation.Status = RecurringOperationStatus.Cancelled;
backgroundOperation.IsRecurring = false;
backgroundOperation.IsNotRecurring = true;
backgroundOperation.IsPaused = false;
backgroundOperation.IsExecuting = false;
backgroundOperation.IsIdle = false;
backgroundOperation.IsCancelled = true;
backgroundOperation.IsNotCancelled = false;
backgroundOperation.CanBeStarted = true;
}
}
/// <summary>
/// Pauses the recurring execution of the operation.
/// Execution can be continued with a call to ResumeRecurring().
/// </summary>
/// <param name="recurringOperation"></param>
public void PauseRecurring(RecurringOperation recurringOperation)
{
// Find a reference to an internal operation
var internalOperation =
recurringOperations.Find(
operation => operation.Name.Equals(recurringOperation.GetName()));
// If found
if (internalOperation != null)
{
// Pause the timer
internalOperation.Timer.Change(Timeout.Infinite, Timeout.Infinite);
// Set status flags of the public facing background operation object
recurringOperation.Status = RecurringOperationStatus.Paused;
recurringOperation.IsRecurring = false;
recurringOperation.IsNotRecurring = true;
recurringOperation.IsPaused = true;
recurringOperation.IsIdle = true;
recurringOperation.IsExecuting = false;
}
}
/// <summary>
/// Creates and/or starts a recurring operation.
/// If an operation has already been started,
/// an exception will be thrown.
/// </summary>
/// <param name="recurringOperation"></param>
/// <param name="interval"></param>
/// <param name="action"></param>
/// <param name="startImmediately"></param>
public void StartRecurring(RecurringOperation recurringOperation, TimeSpan interval, Action action = null, bool startImmediately = false)
{
if (recurringOperation == null)
{
throw new InvalidOperationException(Constants.UninitializedOperationException);
}
if (action != null && recurringOperation.Operation != null)
{
throw new InvalidOperationException(Constants.ActionAlreadySpecifiedException);
}
if (string.IsNullOrWhiteSpace(recurringOperation.GetName()))
{
throw new InvalidOperationException(Constants.UnnamedOperationException);
}
if (recurringOperations.Any(op => op.Name.Equals(recurringOperation.GetName())))
{
throw new InvalidOperationException($"{Constants.RecurringOperationAlreadyRunningException}. Operation name '{recurringOperation.GetName()}'.");
}
// Create a new internal operation object
var internalOperation = new Operation
{
Name = recurringOperation.GetName(),
Interval = interval
};
// Create a callback function for the timer. This function is to be run in specified intervals.
void TimerCallback(object state)
{
// To indicate if a thread has entered a block of code.
bool lockAcquired = false;
try
{
// Try to acquire a lock.
// Sets the value of the lockAcquired, even if the method throws an exception,
// so the value of the variable is a reliable way to test whether the lock has to be released.
Monitor.TryEnter(recurringOperation.CallbackLock, ref lockAcquired);
if (lockAcquired)
{
// Set recurring operation status
recurringOperation.LastRunStart = DateTime.Now;
recurringOperation.IsExecuting = true;
recurringOperation.IsIdle = false;
recurringOperation.Status = RecurringOperationStatus.Executing;
try
{
if (recurringOperation.Operation != null)
{
recurringOperation.Operation?.Invoke();
}
else
{
action?.Invoke();
}
}
catch (Exception ex)
{
// Set the exception
recurringOperation.Exception = ex;
}
finally
{
// Set the time when the run finished
recurringOperation.LastRunFinish = DateTime.Now;
// Set recurring operation status flags
recurringOperation.IsExecuting = false;
recurringOperation.IsIdle = true;
// If not cancelled
if (recurringOperation.Status != RecurringOperationStatus.Cancelled)
{
// Set status to idle
recurringOperation.Status = RecurringOperationStatus.Idle;
}
}
}
}
finally
{
// If a thread acquired the lock
if (lockAcquired)
{
// Release the lock
Monitor.Exit(recurringOperation.CallbackLock);
}
}
} // End of local funtion
// Create and set a timer for the internal operation.
internalOperation.Timer = new Timer(
new TimerCallback(TimerCallback), null, startImmediately ? TimeSpan.Zero : interval, interval);
// Add the internal operation to the Manager's collection of operations
recurringOperations.Add(internalOperation);
// Set the status flags of the public facing recurring operation object
recurringOperation.Status = RecurringOperationStatus.Idle;
recurringOperation.IsRecurring = true;
recurringOperation.IsNotRecurring = false;
recurringOperation.IsPaused = false;
recurringOperation.IsIdle = false;
recurringOperation.CanBeStarted = false;
}