Shows how to fan out to a multiple parallel task chaining sequences using simple C# constructs in Dapr Workflow.

DaprWorkflowParallelTaskChaining.cs

class ParallelTaskChaining : Workflow<string, string>
{
    public override async Task<string> RunAsync(WorkflowContext context, string input)
    {
        // Fan-out to 10 parallel task chains
        List<Task> parallelChains = new();
        for (int i = 0; i < 10; i++)
        {
            // RunSequence encapsulates the task chain as a single task.
            Task chainTask = RunSequence(context);
            parallelChains.Add(chainTask);
        }

        // This Task.WhenAll completes after every task in every chain has completed.
        await Task.WhenAll(parallelChains);
        return "done";
    }

    private static async Task RunSequence(WorkflowContext context)
    {
        // This task chain calls three workflow activities in a row
        await context.CallActivityAsync(nameof(MyActivity));
        await context.CallActivityAsync(nameof(MyActivity));
        await context.CallActivityAsync(nameof(MyActivity));
    }
}

// Simple activity definition that just returns the input (if any)
class MyActivity : WorkflowActivity<string, string>
{
    public override Task<string> RunAsync(WorkflowActivityContext context, string input)
    {
        return Task.FromResult(input);
    }
}