private void CreateWorkflowCore(Guid userId, TimeSpan frequency)
{
// Create new workflow instance.
var parameters = new Dictionary <string, object>
{
{ "UserId", userId },
{ "Delay", frequency },
{ "LastRunTime", DateTime.MinValue },
};
WorkflowInstance workflow = CreateWorkflow <Design.PeriodicWorkflow.PeriodicWorkflow>(parameters);
// Record workflow instance in LinkMe database.
_worker.AttachWorkflow(userId, workflow.InstanceId);
// Start running the workflow.
workflow.Start();
}