Pipeline pattern

The pipeline pattern is commonly used in scenarios where we need to execute the asynchronous tasks in sequence:

Consider a task where we need to create a user record first, then initiate a workflow and send an email. To implement this scenario, we can use the ContinueWith method of TPL. Here is a complete example:

static void Main(string[] args) 
{ 
 
  Task<int> t1 = Task.Factory.StartNew(() =>  
  { return CreateUser(); }); 
 
  var t2=t1.ContinueWith((antecedent) => 
  { return InitiateWorkflow(antecedent.Result); }); 
  var t3 = t2.ContinueWith((antecedant) => 
  { return SendEmail(antecedant.Result); }); 
 
  Console.Read(); 
 
 
} 
 
public static int CreateUser() 
{ 
  //Create user, passing hardcoded user ID as 1 
  Thread.Sleep(1000); 
  Console.WriteLine("User created"); 
  return 1; 
} 
 
public static int InitiateWorkflow(int userId) 
{ 
  //Initiate Workflow 
  Thread.Sleep(1000); 
  Console.WriteLine("Workflow initiates"); 
 
  return userId; 
} 
 
public static int SendEmail(int userId) 
{ 
  //Send email 
  Thread.Sleep(1000); 
  Console.WriteLine("Email sent"); 
 
  return userId; 
}