Control the Modifiability of a Workflow
Back in December 2006, I wrote two posts about dynamically modifying a workflow from the inside and dynamically modifying a workflow from the outside. They're descriptive enough to show how to modify a workflow with either ways but what will you do if you want to prevent a workflow from being modified? In this post, I'll show you how to disable modifiability of a workflow.
To demonstrate how to control the modifiability of a workflow, I use the sample workflow that I wrote to show how to modify a workflow from the inside in the past.
In that workflow I have a delay activity and a code activity in a sequential workflow. After a short delay, my code activity executes a code and creates another code activity on fly and adds it to currently running workflow to generate an output in console.
private void delayActivity1_InitializeTimeoutDuration(object sender, EventArgs e)
{
Console.Title = "Control the Modifiability of a Workflow";
Console.WriteLine("Delay ...");
}
private void codeActivity1_ExecuteCode(object sender, EventArgs e)
{
CodeActivity delay = sender as CodeActivity;
Console.WriteLine(delay.Name);
WorkflowChanges workflowChanges = new WorkflowChanges(this);
CodeActivity codeActivity = new CodeActivity();
codeActivity.Name = "codeActivity2";
codeActivity.ExecuteCode += new EventHandler(codeActivity2_ExecuteCode);
workflowChanges.TransientWorkflow.Activities.Add(codeActivity);
this.ApplyWorkflowChanges(workflowChanges);
}
private void codeActivity2_ExecuteCode(object sender, EventArgs e)
{
CodeActivity codeActivity = sender as CodeActivity;
Console.WriteLine(codeActivity.Name);
Console.ReadLine();
}
Every workflow has a DynamicUpdateCondition property which lets you to enable or disable the modifiability of that workflow. By default workflows are modifiable but to change this behavior you can set a condition for workflow. There are two types of conditions that you can set for a workflow:
- Code Condition: In this case you specify the name of a method where you manage the modifiability of a workflow based on your own logic.
- Declarative Rule Condition: Rule conditions use some expressions to check some constraints based on properties of a workflow. It means that using this option, you can write some expressions and workflow runtime will validate them to enable or disable the modifiability.
You can set the value of DynamicUpdateCondition property in Properties window to one of these two values and set other related values for them based on your choice.
First I use a Code Condition to disable my workflow's modifiability if the TimeoutDuration of my delay activity is more than five seconds. My Code Condition method (which is named UpdateCondition) has two parameters and returns nothing. First parameter is an object and second one is of ConditionalEventArgs type. This latter parameter has a Result boolean property. If you set it to false then workflow isn't modifiable and any attempt to modify it throws an exception on runtime and if you set it to true then workflow is modifiable. Here is the simple logic for my code condition:
private void UpdateCondition(object sender, ConditionalEventArgs e)
{
if (TimeSpan.Compare(this.delayActivity1.TimeoutDuration, new TimeSpan(0, 0, 5)) > 0)
{
e.Result = false;
}
else
{
e.Result = true;
}
}
So if I set my TimoutDuration to ten seconds then will get an exception on runtime as you see:
Similarly I could use a Declarative Rule Condition. In this case, workflow is modifiable until an expression is validated as true otherwise it will fail to modify. For example, I create a condition to check if the number of activities in current workflow is zero then make it modifiable.
In my case workflow is not modifiable because the number of activities is not zero.
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1 Comment : 06.18.07
#1
spitraberg
12.06.2007 @ 5:42 AM