AsyncSerialTask

   The syntax of the AsyncSerialTask is pretty abstruse.  Here's one way to implement this - 

 private void LoadData(string userID) {
   //Guid myToken = Guid.NewGuid();
   //object[] param = {userID};
   AsyncSerialTask.Create<string>()
        .AddAsyncInvokeServerMethod<object, object, InvokeServerMethodEventArgs>(m_mgr, 
  "C2NetDomainModel.EntCustomer,C2NetDomainModel", "GetCustomerIDs",
   inputArg=> new object[] {inputArg})
        .AddAsyncQuery(args => GotCustomerIds(args))
        .AddExceptionHandler(exArgs => WriteMessage(exArgs.Exception.Message))
        .Execute(userID, (completionArgs) => GotCustomers(completionArgs.Result));
  }
  public IEntityQuery<EntCustomer> GotCustomerIDs( InvokeServerMethodEventArgs args )
  {
    int[] customerIDs = ((C2NetDomainModel.IntIDs)(args.Result)).p_ids;
    var customerQ = m_mgr.EntCustomerSet
           .OrderBy( c => c.p_name )
           .WhereIn( c => c.p_customerID , customerIDs );
    return customerQ;
  }
  private void GotCustomers(EntityFetchedEventArgs<EntCustomer> args)
  {
    foreach( EntCustomer c in args.Result ) 
    {
     _customers.Add(c); 
    } 
    // Set CurrentItem to first Customer so form will flesh out 
    if (_customers.Count > 0) {
     _customerDataForm.CurrentItem = _customers[0];
    }
    ReportFetchCount(args.Result, "Customer");
  }

Things to note - 
1) When you create the task you can specify the type of the input argument, in this case a string.
2) A few of the overloads for AddAsyncInvokeServerMethod take a lambda as a final argument.  This is what we're using here: it takes a string (the input to the task) and returns an object array containing that string.
3) AddAsyncInvokeServerMethod defines T0, T1 and T2 and I admit I don't know why there are 3 type arguments instead of two.  But anyway, T0 and T1 should be the input type (and can be 'object' if no input is provided, and T2 is 'InvokeServerMethodArgs'. 
4) Exceptions are handled a bit differently with an AsyncSerialTask, and you should add an exception handler to the task to trap any errors.
5) GotCustomerIDs takes the InvokeServerMethodEventArgs and builds a query, which it then returns as the async query to be run next.
6) task.Execute accepts an input argument, in this case the string userID.  This is passed to the first action in the task.
7) At completion, the results of the last action are available in the Result property.  This is passed to the GotCustomers method.