Introduction

 

Developers can easily make use of task management features offered by Aspose.Workflow. In this topic, we will discuss the task management based on a process instance or a user. To manage something, we need to have that thing first. So, before managing workflow tasks, we need to retrieve these tasks first. There are two ways to retrieve workflow tasks as follows:

 

• Tasks associated with a process instance
• Tasks associated with a user

 

Tasks Based on a Process Instance

 

Developers can obtain a list of all workflow tasks associated to any process instance by calling the GetAllTasks method of IProcessInstance interface. GetAllTasks method takes a boolean parameter, true or false. If you want only pending tasks, just pass true otherwise false to retreive all tasks as shown below in the example.

 

Example:

 

[C#]

 

//Instantiate an object of EngineManager

EngineManager manager = EngineManager.Instance;

 

//Configure the EngineManager object

manager.Configure();

 

//Create an object of IEngine interface

IEngine engine = manager.Engine;

 

//Login to the Aspose.Workflow engine

engine.Login("aspose","aspose");

 

//Create an instance of IInstanceAdmin interface

IInstanceAdmin instanceAdmin = engine.InstanceAdmin;

 

//Access a specific process instance by passing its instance ID

IProcessInstance instance = instanceAdmin.GetProcessInstance(

                                "1_TestInstance_TestInstance_Wor1");

 

//Retrieving all tasks related to the specified process instance

ITask[] tasks=instance.GetAllTasks(false);

 

[VB.NET]

 

'Instantiate an object of EngineManager

Dim manager As EngineManager =  EngineManager.Instance

 

'Configure the EngineManager object

manager.Configure()

 

'Create an object of IEngine interface

Dim engine As IEngine =  manager.Engine

 

'Login to the Aspose.Workflow engine

engine.Login("aspose","aspose")

 

'Create an instance of IInstanceAdmin interface

Dim instanceAdmin As IInstanceAdmin =  engine.InstanceAdmin

 

'Access a specific process instance by passing its instance ID

Dim instance As IProcessInstance =  instanceAdmin.GetProcessInstance(

                                        "1_TestInstance_TestInstance_Wor1")

 

'Retrieving all tasks related to the specified process instance

Dim tasks() As ITask = instance.GetAllTasks(False)

 

Tasks Based on a User

 

For obtaining all tasks associated to some user, developers would need to call GetAllTasks method of IEngine.Worklist object but before calling this method, it would be needed to connect to Aspose.Workflow engine using the Username and Password of the desired user. For further details, refer to Access all tasks related to a user .

 

Example:

 

[C#]

 

//Login to Aspose.Workflow engine for user "jack"

engine.Login("jack","baldwin");

 

//Retrieving all tasks associated to "jack"

ITask[] tasks=engine.Worklist.GetAllTasks();

 

[VB.NET]

 

'Login to Aspose.Workflow engine for user "jack"

engine.Login("jack","baldwin")

 

'Retrieving all tasks associated to "jack"

Dim tasks() As ITask = engine.Worklist.GetAllTasks()

 

Task Management

 

All kinds of workflow tasks (either associated to a process instance or a user) are managed in the same way using IEngine.Worklist object, which provides us an instance of IWorklist2 interface. IWorklist2 interface is extended from IWorklist interface that has many methods to manage tasks in a variety of ways as follows:

 

• Accepting Tasks
• Releasing Tasks
• Completing Tasks
• Re-assigning Tasks

 

Accepting Tasks

 

Whenever a user wants to work on some workflow task, he needs to accept that task first by calling AcceptTask method of IEngine.Worklist object. After a task is accepted by some user, it is assigned to that one and becomes invisible to other users disallowing them to work on that task.

 

Example:

 

[C#]

 

//Accepting a workflow task

engine.Worklist.AcceptTask(task);

 

[VB.NET]

 

'Accepting a workflow task

engine.Worklist.AcceptTask(task)

 

Before completing, releasing or reassigning a task, it's better to check that whether that task has already been accepted or not. It can be done by calling IsTaskAccepted method of IEngine.Worklist object, which takes the task ID and returns a boolean value to indicate that the specified task is already accepted or not.

 

Example:

 

[C#]

 

//Accepting a workflow task if it is not already accepted

if(!engine.Worklist.IsTaskAccepted(task.Id))

{

   engine.Worklist.AcceptTask(task);

}

 

[VB.NET]

 

'Accepting a workflow task if it is not already accepted

If Not engine.Worklist.IsTaskAccepted(task.Id) Then

   engine.Worklist.AcceptTask(task)

End If

 

Releasing Tasks

 

For releasing workflow tasks due to any reason, developers can make use of ReleaseTask method of IEngine.Worklist object as shown below in the code snippet.

 

Example:

 

[C#]

 

//Accepting a workflow task if it is not already accepted

if(!engine.Worklist.IsTaskAccepted(task.Id))

{

   engine.Worklist.AcceptTask(task);

}

 

//Releasing a workflow task

engine.Worklist.ReleaseTask(task);

 

[VB.NET]

 

'Accepting a workflow task if it is not already accepted

If Not engine.Worklist.IsTaskAccepted(task.Id) Then

   engine.Worklist.AcceptTask(task)

End If

 

'Releasing a workflow task

engine.Worklist.ReleaseTask(task)

 

Completing Tasks

 

After a user finishes his work required for some workflow task, user can call CompleteTask method of IEngine.Worklist object to complete that task as shown below in the code snippet. CompleteTask method also allows users to pass the instance variables for the task in the form of an IDictionary object. These variables are used for task completion. But, if you don't want to pass these instance variables then simply pass null instead of IDictionary object.

 

Completing Task Without Setting Variables

 

Example:

 

[C#]

 

//Accepting a workflow task if it is not already accepted

if(!engine.Worklist.IsTaskAccepted(task.Id))

{

   engine.Worklist.AcceptTask(task);

}

 

//Complete task but don't set the instance variables

engine.Worklist.CompleteTask(task,null);

 

[VB.NET]

 

'Accepting a workflow task if it is not already accepted

If Not engine.Worklist.IsTaskAccepted(task.Id) Then

   engine.Worklist.AcceptTask(task)

End If

 

'Complete task but don't set the instance variables

engine.Worklist.CompleteTask(task,Nothing)

 

Completing Task With Setting Variables

 

Example:

 

[C#]

 

//Accepting a workflow task if it is not already accepted

if(!engine.Worklist.IsTaskAccepted(task.Id))

{

   engine.Worklist.AcceptTask(task);

}

 

//Set variables

IDictionary vars = new Hashtable();

vars["Var1"] = "Value1";

vars["Var2"] = "Value2";

 

//Complete task and pass variables

engine.Worklist.CompleteTask(task,vars);

 

[VB.NET]

 

'Accepting a workflow task if it is not already accepted

If Not engine.Worklist.IsTaskAccepted(task.Id) Then

   engine.Worklist.AcceptTask(task)

End If

 

'Set variables

Dim vars As IDictionary =  New Hashtable()

vars("Var1") = "Value1"

vars("Var2") = "Value2"

 

'Complete task and pass variables

engine.Worklist.CompleteTask(task,vars)

 

Re-assigning Tasks

 

If a user wants some other person to work on a workflow task then ReassignTask method of IEngine.Worklist object will be called by the user as shown below in the code snippet.

 

Example:

 

[C#]

 

//Accepting a workflow task if it is not already accepted

if(!engine.Worklist.IsTaskAccepted(task.Id))

{

   engine.Worklist.AcceptTask(task);

}

 

//Reassign the task to "james"

engine.Worklist.ReassignTask(task, "james");

 

[VB.NET]

 

'Accepting a workflow task if it is not already accepted

If Not engine.Worklist.IsTaskAccepted(task.Id) Then

   engine.Worklist.AcceptTask(task)

End If

 

'Reassign the task to "james"

engine.Worklist.ReassignTask(task, "james")