How to compose activities and build/run workflow dynamically?

[zh6335901]

Hi, Thank for your great project!
Does elsa support compose activities and build/run workflow dynamically? I can't find some related content in documentation.
In my application, I want to compose activities dynamically by some domain models, And then build it and run it.

[sfmskywalker]

With Elsa 2, I don't think it's possible without making some drastic changes.
With Elsa 3 on the other hand, this can be done natively. There, you could do something like this:

// Some application code

var myCompositeActivity = new Composite
{
   Root = new Sequence
   {
      new WriteLine("Wazzaa")
   }
};

var workflow = new Workflow
{
   Root = myCompositeActivity
}

workflowRunner.RunAsync(workflow);

I realize this doesn't help you now though.
Elsa 3 early preview should be available around May/June.

[sfmskywalker]

Actually, I may have spoken too soon about this not being supported by Elsa 2.

In Elsa 2, what you might do is create your workflow model using WorkflowDefinition, ActivityDefinition and CompositeActivityDefinition for composite activities.

For example:

// Define a workflow.
var workflowDefinition = new WorkflowDefinition
{
    Id = "1",
    DefinitionId = "SampleWorkflow",
    Version = 1,
    IsPublished = true,
    IsLatest = true,
    PersistenceBehavior = WorkflowPersistenceBehavior.Suspended,
    Activities = new[]
    {
        WriteLine("write-line-1", "==Composite Activities Demo=="),
        new CompositeActivityDefinition
        {
            ActivityId = "composite-1",
            Activities = new[]
            {
                WriteLine("write-line-2", "Line 1 of composite activity."),
                WriteLine("write-line-3", "Line 2 of composite activity."),
            },
            Connections = new[]
            {
                new ConnectionDefinition("write-line-2", "write-line-3", OutcomeNames.Done)
            }
        },
        WriteLine("write-line-4", "==End=="),
    },
    Connections = new[]
    {
        new ConnectionDefinition("write-line-1", "composite-1", OutcomeNames.Done),
        new ConnectionDefinition("composite-1", "write-line-4", OutcomeNames.Done),
    }
};

// Serialize workflow definition to JSON.
var serializer = services.GetRequiredService<IContentSerializer>();
var json = serializer.Serialize(workflowDefinition);

// Deserialize workflow definition from JSON.
var deserializedWorkflowDefinition = serializer.Deserialize<WorkflowDefinition>(json);

// Materialize workflow.
var materializer = services.GetRequiredService<IWorkflowBlueprintMaterializer>();
var workflowBlueprint = await materializer.CreateWorkflowBlueprintAsync(deserializedWorkflowDefinition);

// Execute workflow.
var workflowRunner = services.GetRequiredService<IStartsWorkflow>();
await workflowRunner.StartWorkflowAsync(workflowBlueprint);

I even have an example of this here 😄

[zh6335901]

Thanks, I will try it😄