---
product: Chilkat
product_version: 11.7.0
language: delphidll
language_label: Delphi DLL
class: TaskChain
license: bundle
deprecated: false
reference_html: https://www.chilkatsoft.com/refdoc/dd_CkTaskChainRef.html
---
# Chilkat TaskChain — Delphi DLL — v11.7.0

> Chilkat 11.7.0 · language=delphidll · class=TaskChain
> Other versions: replace `11.7.0` in this URL. Other languages: `https://www.chilkatsoft.com/ai-docs/v/11.7.0/<lang>/classes/TaskChain.md`.
> Language-wide rules (install, unlock, error model, strings/bytes): `https://www.chilkatsoft.com/ai-docs/v/11.7.0/delphidll/guide.md`.

## Purpose

**Run multiple asynchronous Chilkat tasks in a defined sequence.**

`Chilkat.TaskChain` manages a sequence of `Chilkat.Task` objects and runs them one after another. It is useful when multiple asynchronous Chilkat operations must execute in a predictable order while still allowing the entire chain to be started, monitored, waited on, canceled, or run synchronously. A task chain can stop when a task fails, or continue depending on the configured behavior.

**Sequential async workflow**

Append multiple `Task` objects and run them in order when one operation must finish before the next begins.

**Chain-level execution**

Start the entire chain, run it synchronously, wait for completion, or cancel the chain as a single coordinated operation.

**Monitor progress and status**

Inspect whether the chain is live, finished, inert, canceled, failed, or still running.

**Access individual tasks**

Retrieve tasks by index after execution to inspect each task's status, success flag, error text, and result.

**Stop-on-failure control**

Use `StopOnFailedTask` to control whether the chain stops at the first failed task or continues to later tasks.

**Diagnostics**

Use task and chain status information together with `LastErrorText` and each task's result details to troubleshoot ordered async workflows.

**Common pattern:** Create the individual async tasks, append them to a `TaskChain` in the required order, set `StopOnFailedTask` as appropriate, run the chain, wait for completion, then inspect each task's success status and result. Use `TaskChain` when operations must run sequentially; use individual `Task` objects when each async operation can be managed on its own.

For an extended overview, see [TaskChain Class Overview](https://www.chilkatsoft.com/taskchain_class_overview.asp).

## Object creation, unlocking and error handling

**Create/Dispose**

```pascal
var
myObject: HCkTaskChain;

begin
myObject := CkTaskChain_Create();

// ...

CkTaskChain_Dispose(myObject);
end;
```

`function CkTaskChain_Create: HCkTaskChain; stdcall;`

Creates an instance of the HCkTaskChain object and returns a handle (i.e. a Pointer). The handle is passed in the 1st argument for the functions listed on this page.

`procedure CkTaskChain_Dispose(handle: HCkTaskChain); stdcall;`

Objects created by calling CkTaskChain_Create must be freed by calling this method. A memory leak occurs if a handle is not disposed by calling this function.

Call `Global.UnlockBundle` once at the start of the program, before using this or any other Chilkat class. Any string unlocks a fully functional 30-day trial; a purchased unlock code is used in production. See `guide.md` for the exact code in Delphi DLL.

## Members common to every Chilkat class

Documented once per language in `common-members.md`; listed here so this page is self-contained.

| Property | Signature | Access | Meaning |
|---|---|---|---|
| `DebugLogFilePath` | `procedure CkTaskChain_getDebugLogFilePath(objHandle: HCkTaskChain; outPropVal: HCkString); stdcall; procedure CkTaskChain_putDebugLogFilePath(objHandle: HCkTaskChain; newPropVal: PWideChar); stdcall; function CkTaskChain__debugLogFilePath(objHandle: HCkTaskChain): PWideChar; stdcall;` | read/write | If set to a file path, this property logs the LastErrorText of each Chilkat method or property call to the specified file. |
| `LastErrorHtml` | `procedure CkTaskChain_getLastErrorHtml(objHandle: HCkTaskChain; outPropVal: HCkString); stdcall; function CkTaskChain__lastErrorHtml(objHandle: HCkTaskChain): PWideChar; stdcall;` | read-only | Provides HTML-formatted information about the last called method or property. |
| `LastErrorText` | `procedure CkTaskChain_getLastErrorText(objHandle: HCkTaskChain; outPropVal: HCkString); stdcall; function CkTaskChain__lastErrorText(objHandle: HCkTaskChain): PWideChar; stdcall;` | read-only | Provides plain text information about the last called method or property. |
| `LastErrorXml` | `procedure CkTaskChain_getLastErrorXml(objHandle: HCkTaskChain; outPropVal: HCkString); stdcall; function CkTaskChain__lastErrorXml(objHandle: HCkTaskChain): PWideChar; stdcall;` | read-only | Provides XML-formatted information about the last called method or property. |
| `LastMethodSuccess` | `function CkTaskChain_getLastMethodSuccess(objHandle: HCkTaskChain): wordbool; stdcall; procedure CkTaskChain_putLastMethodSuccess(objHandle: HCkTaskChain; newPropVal: wordbool); stdcall;` | read/write | Indicates the success or failure of the most recent method call: `True` means success, `False` means failure. |
| `VerboseLogging` | `function CkTaskChain_getVerboseLogging(objHandle: HCkTaskChain): wordbool; stdcall; procedure CkTaskChain_putVerboseLogging(objHandle: HCkTaskChain; newPropVal: wordbool); stdcall;` | read/write | If set to `True`, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. |
| `Version` | `procedure CkTaskChain_getVersion(objHandle: HCkTaskChain; outPropVal: HCkString); stdcall; function CkTaskChain__version(objHandle: HCkTaskChain): PWideChar; stdcall;` | read-only | Version of the component/library, such as "10.1.0" |

## Member index

| Member | Kind | Signature |
|---|---|---|
| `Finished` | property, read-only | `function CkTaskChain_getFinished(objHandle: HCkTaskChain): wordbool; stdcall;` |
| `HeartbeatMs` | property, read/write | `function CkTaskChain_getHeartbeatMs(objHandle: HCkTaskChain): Integer; stdcall; procedure CkTaskChain_putHeartbeatMs(objHandle: HCkTaskChain; newPropVal: Integer); stdcall;` |
| `Inert` | property, read-only | `function CkTaskChain_getInert(objHandle: HCkTaskChain): wordbool; stdcall;` |
| `Live` | property, read-only | `function CkTaskChain_getLive(objHandle: HCkTaskChain): wordbool; stdcall;` |
| `NumTasks` | property, read-only | `function CkTaskChain_getNumTasks(objHandle: HCkTaskChain): Integer; stdcall;` |
| `Status` | property, read-only | `procedure CkTaskChain_getStatus(objHandle: HCkTaskChain; outPropVal: HCkString); stdcall; function CkTaskChain__status(objHandle: HCkTaskChain): PWideChar; stdcall;` |
| `StatusInt` | property, read-only | `function CkTaskChain_getStatusInt(objHandle: HCkTaskChain): Integer; stdcall;` |
| `StopOnFailedTask` | property, read/write | `function CkTaskChain_getStopOnFailedTask(objHandle: HCkTaskChain): wordbool; stdcall; procedure CkTaskChain_putStopOnFailedTask(objHandle: HCkTaskChain; newPropVal: wordbool); stdcall;` |
| `Append` | method | `function CkTaskChain_Append(objHandle: HCkTaskChain;     task: HCkTask): wordbool; stdcall;` |
| `Cancel` | method | `function CkTaskChain_Cancel(objHandle: HCkTaskChain): wordbool; stdcall;` |
| `GetTask` | method | `function CkTaskChain_GetTask(objHandle: HCkTaskChain;     index: Integer): HCkTask; stdcall;` |
| `Run` | method | `function CkTaskChain_Run(objHandle: HCkTaskChain): wordbool; stdcall;` |
| `RunSynchronously` | method | `function CkTaskChain_RunSynchronously(objHandle: HCkTaskChain): wordbool; stdcall;` |
| `SleepMs` | method | `procedure CkTaskChain_SleepMs(objHandle: HCkTaskChain;     numMs: Integer) stdcall;` |
| `Wait` | method | `function CkTaskChain_Wait(objHandle: HCkTaskChain;     maxWaitMs: Integer): wordbool; stdcall;` |

## Properties

### TaskChain.Finished

`Chilkat 11.7.0 · delphidll · TaskChain · Finished · property · read-only · since 9.5.0.52`

```pascal
function CkTaskChain_getFinished(objHandle: HCkTaskChain): wordbool; stdcall;
```

`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.

### TaskChain.HeartbeatMs

`Chilkat 11.7.0 · delphidll · TaskChain · HeartbeatMs · property · read/write · since 9.5.0.52`

```pascal
function CkTaskChain_getHeartbeatMs(objHandle: HCkTaskChain): Integer; stdcall;
procedure CkTaskChain_putHeartbeatMs(objHandle: HCkTaskChain; newPropVal: Integer); stdcall;
```

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.

### TaskChain.Inert

`Chilkat 11.7.0 · delphidll · TaskChain · Inert · property · read-only · since 9.5.0.52`

```pascal
function CkTaskChain_getInert(objHandle: HCkTaskChain): wordbool; stdcall;
```

`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.

### TaskChain.Live

`Chilkat 11.7.0 · delphidll · TaskChain · Live · property · read-only · since 9.5.0.52`

```pascal
function CkTaskChain_getLive(objHandle: HCkTaskChain): wordbool; stdcall;
```

`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.

### TaskChain.NumTasks

`Chilkat 11.7.0 · delphidll · TaskChain · NumTasks · property · read-only · since 9.5.0.52`

```pascal
function CkTaskChain_getNumTasks(objHandle: HCkTaskChain): Integer; stdcall;
```

The number of tasks contained within the task chain.

### TaskChain.Status

`Chilkat 11.7.0 · delphidll · TaskChain · Status · property · read-only · since 9.5.0.52`

```pascal
procedure CkTaskChain_getStatus(objHandle: HCkTaskChain; outPropVal: HCkString); stdcall;
function CkTaskChain__status(objHandle: HCkTaskChain): PWideChar; stdcall;
```

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.

### TaskChain.StatusInt

`Chilkat 11.7.0 · delphidll · TaskChain · StatusInt · property · read-only · since 9.5.0.52`

```pascal
function CkTaskChain_getStatusInt(objHandle: HCkTaskChain): Integer; stdcall;
```

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.

### TaskChain.StopOnFailedTask

`Chilkat 11.7.0 · delphidll · TaskChain · StopOnFailedTask · property · read/write · since 9.5.0.52`

```pascal
function CkTaskChain_getStopOnFailedTask(objHandle: HCkTaskChain): wordbool; stdcall;
procedure CkTaskChain_putStopOnFailedTask(objHandle: HCkTaskChain; newPropVal: wordbool); stdcall;
```

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`.

## Methods

### TaskChain.Append

`Chilkat 11.7.0 · delphidll · TaskChain · Append · method · since 9.5.0.52`

```pascal
function CkTaskChain_Append(objHandle: HCkTaskChain;
    task: HCkTask): wordbool; stdcall;
```

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.

### TaskChain.Cancel

`Chilkat 11.7.0 · delphidll · TaskChain · Cancel · method · since 9.5.0.52`

```pascal
function CkTaskChain_Cancel(objHandle: HCkTaskChain): wordbool; stdcall;
```

Cancels execution of the asynchronous task chain.

Returns True for success, False for failure.

### TaskChain.GetTask

`Chilkat 11.7.0 · delphidll · TaskChain · GetTask · method · since 9.5.0.52`

```pascal
function CkTaskChain_GetTask(objHandle: HCkTaskChain;
    index: Integer): HCkTask; stdcall;
```

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

Returns `nil` on failure

### TaskChain.Run

`Chilkat 11.7.0 · delphidll · TaskChain · Run · method · since 9.5.0.52`

```pascal
function CkTaskChain_Run(objHandle: HCkTaskChain): wordbool; stdcall;
```

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.

### TaskChain.RunSynchronously

`Chilkat 11.7.0 · delphidll · TaskChain · RunSynchronously · method · since 9.5.0.52`

```pascal
function CkTaskChain_RunSynchronously(objHandle: HCkTaskChain): wordbool; stdcall;
```

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.

### TaskChain.SleepMs

`Chilkat 11.7.0 · delphidll · TaskChain · SleepMs · method · since 9.5.0.52`

```pascal
procedure CkTaskChain_SleepMs(objHandle: HCkTaskChain;
    numMs: Integer) stdcall;
```

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

### TaskChain.Wait

`Chilkat 11.7.0 · delphidll · TaskChain · Wait · method · since 9.5.0.52`

```pascal
function CkTaskChain_Wait(objHandle: HCkTaskChain;
    maxWaitMs: Integer): wordbool; stdcall;
```

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.

## Events and callbacks

### TaskChain.AbortCheck (event)

`Chilkat 11.7.0 · delphidll · TaskChain · AbortCheck · event`

```pascal
function MyAbortCheck(): Integer; cdecl;
```

Enables a method call to be aborted by triggering the AbortCheck event at intervals defined by the `HeartbeatMs` property. If HeartbeatMs is set to its default value of 0, no events will occur. For instance, set HeartbeatMs to 200 to trigger 5 AbortCheck events per second. Return `True` to abort; return `False` to continue (not abort)

### TaskChain.PercentDone (event)

`Chilkat 11.7.0 · delphidll · TaskChain · PercentDone · event`

```pascal
function MyPercentDone(pctDone: Integer): Integer; cdecl;
```

This provides the percentage completion for any method involving network communications or time-consuming processing, assuming the progress can be measured as a percentage. This event is triggered only when it's possible and logical to express the operation's progress as a percentage. The `pctDone` argument will range from 1 to 100. For methods that finish quickly, the number of PercentDone callbacks may vary, but the final callback will have `pctDone` equal to 100. For longer operations, callbacks will not exceed one per percentage point (e.g., 1, 2, 3, ..., 98, 99, 100).

The PercentDone callback also acts as an `AbortCheck` event. For fast methods where PercentDone fires, an AbortCheck event may not trigger since the PercentDone callback already provides an opportunity to abort. For longer operations, where time between PercentDone callbacks is extended, AbortCheck callbacks enable more responsive operation termination.

Return `True` to abort; return `False` to continue (not abort)

### TaskChain.ProgressInfo (event)

`Chilkat 11.7.0 · delphidll · TaskChain · ProgressInfo · event`

```pascal
procedure MyProgressInfo(name: PWideChar; value: PWideChar) cdecl;
```

This event callback provides `tag name`/value pairs that detail what occurs during a method call. To discover existing tag names, create code to handle the event, emit the pairs, and review them. Most tag names are self-explanatory.

Note: Some Chilkat methods don't fire any ProgressInfo events.

### TaskChain.TaskCompleted (event)

`Chilkat 11.7.0 · delphidll · TaskChain · TaskCompleted · event`

```pascal
procedure MyTaskCompleted(task: HCkTask) cdecl;
```

Called from the background thread when an asynchronous task completes.

## Related classes

[`Task`](https://www.chilkatsoft.com/ai-docs/v/11.7.0/delphidll/classes/Task.md)