TaskChain

If set to a file path, causes each Chilkat method or property call to automatically append it's LastErrorText to the specified log file. The information is appended such that if a hang or crash occurs, it is possible to see the context in which the problem occurred, as well as a history of all Chilkat calls up to the point of the problem. The VerboseLogging property can be set to provide more detailed information.

This property is typically used for debugging the rare cases where a Chilkat method call hangs or generates an exception that halts program execution (i.e. crashes). A hang or crash should generally never happen. The typical causes of a hang are:

1. a timeout related property was set to 0 to explicitly indicate that an infinite timeout is desired,
2. the hang is actually a hang within an event callback (i.e. it is a hang within the application code), or
3. there is an internal problem (bug) in the Chilkat code that causes the hang.

True if the task status is "canceled", "aborted", or "completed". A task chain can only reach the "canceled" status if it was activated via the Run method, made it onto the internal thread pool thread's queue, was waiting for a pool thread to become available, and was then canceled prior to the task actually starting.

The number of milliseconds between each AbortCheck event callback. The AbortCheck callback allows an application to abort the Wait method. If HeartbeatMs is 0 (the default), no AbortCheck event callbacks will fire. Note: An asynchronous task chain running in a background thread (in one of the thread pool threads) does not fire events. The task chain's event callbacks pertain only to the Wait method.

True if the task status is "empty" or "loaded". When a task chain is inert, it has been loaded but is not scheduled to run yet.

Provides information in HTML format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

Provides information in plain-text format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

Provides information in XML format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

Indicate whether the last method call succeeded or failed. A value of True indicates success, a value of False indicates failure. This property is automatically set for method calls. It is not modified by property accesses. The property is automatically set to indicate success for the following types of method calls:

• Any method that returns a string.
• Any method returning a Chilkat object, binary bytes, or a date/time.
• Any method returning a standard boolean status value where success = True and failure = False.
• Any method returning an integer where failure is defined by a return value less than zero.

Note: Methods that do not fit the above requirements will always set this property equal to True. For example, a method that returns no value (such as a "void" in C++) will technically always succeed.

True if the task status is "queued" or "running". When a task chain is live, it is either already running, or is on the thread pool thread's queue waiting for a thread to become available.

The number of tasks contained within the task chain.

The current status of the task chain. Possible values are:

• "empty" -- No tasks have yet been appended to the task chain.
• "loaded" -- The task chain has been loaded (appended) with one or more task objects.
• "queued" -- The task chain is in the thread pool's queue of tasks awaiting to be run.
• "running" -- The task chain is currently running.
• "canceled" -- The task chain was canceled before it entered the "running" state.
• "aborted" -- The task chain was canceled while it was in the running state.
• "completed" -- The task chain completed.

The current status of the task as an integer value. Possible values are:

• 1 -- "empty" -- No tasks have yet been appended to the task chain.
• 2 -- "loaded" -- The task chain has been loaded (appended) with one or more task objects.
• 3 -- "queued" -- The task chain is in the thread pool's queue of tasks awaiting to be run.
• 4 -- "running" -- The task chain is currently running.
• 5 -- "canceled" -- The task chain was canceled before it entered the "running" state.
• 6 -- "aborted" -- The task chain was canceled while it was in the running state.
• 7 -- "completed" -- The task chain completed.

If True then stops execution of the task chain if any individual task fails. Task failure is defined by the standard LastMethodSuccess property. If False, then all of the tasks in the chain will be run even if some fail. The default value of this property is True.

If set to True, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is False. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.

Version of the component/library, such as "9.5.0.94"

Appends a task to the task chain. Can fail if the task is already part of another chain. (A task can only be part of a single chain.)

Returns True for success, False for failure.

Cancels execution of the asynchronous task chain.

Returns True for success, False for failure.

Returns the Nth task in the chain. The 1st task is at index 0.

Returns Nothing on failure

Queues the task chain to run on the internal Chilkat thread pool. Each task in the chain will run, one after the other.

Returns True for success, False for failure.

Runs the task chain synchronously. Then this method returns after all the tasks in the chain have been run.

Returns True for success, False for failure.

Convenience method to force the calling thread to sleep for a number of milliseconds.

Waits for the task chain to complete. Returns when all of the tasks in the chain have completed, or after maxWaitMs milliseconds have elapsed. (A maxWaitMs value of 0 is to wait indefinitely.) Returns (False) if the task chain has not yet been started by calling the Run method, or if the maxWaitMs expired. If the task chain completed, was already completed, was canceled, or aborted, then this method returns True.

Returns True for success, False for failure.

Provides the opportunity for a method call to be aborted. The AbortCheck event is fired periodically based on the value of the HeartbeatMs property. If HeartbeatMs is 0, then no AbortCheck events will fire. As an example, to fire 5 AbortCheck events per second, set the HeartbeatMs property equal to 200.

Args are passed using Chilkat.AbortCheckEventArgs

Event callback implementation:

Dim WithEvents taskchain As Chilkat.TaskChain

Private Sub taskchain_OnAbortCheck(sender As Object, args As Chilkat.AbortCheckEventArgs) Handles taskchain.OnAbortCheck

    ...

End Sub

Provides the percentage completed for any method that involves network communications or time-consuming processing (assuming it is a method where a percentage completion can be measured). This event is only fired when it is possible to know a percentage completion, and when it makes sense to express the operation as a percentage completed. The pctDone argument will have a value from 1 to 100. For operations (Chilkat method calls) that complete very quickly, the number of PercentDone callbacks will vary, but the final callback should have a value of 100. For long running operations, no more than one callback per percentage point will occur (for example: 1, 2, 3, ... 98, 99, 100).

The PercentDone callback counts as an AbortCheck event. For method calls that complete quickly such that PercentDone events fire, it may be that AbortCheck events don't fire because the opportunity to abort is already provided in the PercentDone callback. For time consuming operations, where the amount of time between PercentDone callbacks are long, AbortCheck callbacks may be used to allow for the operation to be aborted in a more responsive manner.

The abort output argument provides a means for aborting the operation. Setting it to True will cause the method to abort and return a failed status (or whatever return value indicates failure).

Args are passed using Chilkat.PercentDoneEventArgs

Event callback implementation:

Dim WithEvents taskchain As Chilkat.TaskChain

Private Sub taskchain_OnPercentDone(sender As Object, args As Chilkat.PercentDoneEventArgs) Handles taskchain.OnPercentDone

    ...

End Sub

A general name/value event that provides information about what is happening during a method call. To find out what information is available, write code to handle this event and log the name/value pairs. Most are self-explanatory.

Args are passed using Chilkat.ProgressInfoEventArgs

Event callback implementation:

Dim WithEvents taskchain As Chilkat.TaskChain

Private Sub taskchain_OnProgressInfo(sender As Object, args As Chilkat.ProgressInfoEventArgs) Handles taskchain.OnProgressInfo

    ...

End Sub

Called in the background thread when an asynchronous task completes.

Args are passed using Chilkat.TaskCompletedEventArgs

Event callback implementation:

Dim WithEvents taskchain As Chilkat.TaskChain

Private Sub taskchain_OnTaskCompleted(sender As Object, args As Chilkat.TaskCompletedEventArgs) Handles taskchain.OnTaskCompleted

    ...

End Sub