OrchestrateWorkflow.cs

[FunctionName("OrchestrateWorkflow")]
public static async Task<List<string>> RunOrchestrator(
    [OrchestrationTrigger] IDurableOrchestrationContext context)
{
    var outputs = new List<string>();

    // Call a task and wait for the result.
    outputs.Add(await context.CallActivityAsync<string>("FetchData", "recordId"));
    
    // Fan out parallel tasks
    var tasks = new List<Task<string>>
    {
        context.CallActivityAsync<string>("ProcessData", "param1"),
        context.CallActivityAsync<string>("ProcessData", "param2")
    };
    var results = await Task.WhenAll(tasks);
    outputs.AddRange(results);

    return outputs;
}