Best practices for converting WCF calls to async WCF calls

Question

I am running into issues when trying to convert all my normal WCF calls to async WCF calls. I'm finding I have a refactor a lot of code and not sure exactly how to do it. I have used the method that I found here but running into issues where I need things to happen in order.

private void btnSave_Click(object sender, RoutedEventArgs e)
{

  List<Item> itemList = GetList();
  foreach(Item i in itemList)
  {
    DoSomeWork(i);

    if(i.SomeID == 0)
    {      
       DoSomeMoreWork(i);  
    }

    UpdateRecord(i)  // this can't execute until the above code is complete

  }
}

private void DoSomeWork(Item i)
{
  // call async method
}

private void DoSomeMoreWork(i)
{
  // call async method
}

private void UpdateRecord(item i)
{
  // call async method
}

What is the best way to refactor code to work in an asyncronous way, or do I need to completely rethink my logic? Do I really have to insert counters and switches everywhere to make sure certain things are done before other things execute?

EDIT: The reason I'm doing this is in the next couple months, we are converting this WPF application to Silverlight, which requires async calls. So I'm trying to convert our regular WCF calls to async in preparation. I'm finding it requires a different way of thinking.

Answer 1

For what you're doing, I'd say the real place to handle things is to make a single call to the service per item, not 3.

Preferably, if the list of items is not huge, make a single call to the service with the whole list...

private void btnSave_Click(object sender, RoutedEventArgs e)
{  
    List<Item> itemList = GetList();  
    foreach(Item i in itemList)  
    {    
        DoAllTheWorkAndUpdate(i);    
    }
}

or...

private void btnSave_Click(object sender, RoutedEventArgs e)
{  
    List<Item> itemList = GetList();  
    foreach(Item i in itemList)  
    {    
        if(i.Id == 0)
        {
            DoLotsOfWorkAndUpdate(i);
        }
        else
        {
            DoSomeWorkAndUpdate(i);
        }

    }
}

or...

private void btnSave_Click(object sender, RoutedEventArgs e)
{  
    List<Item> itemList = GetList();  
    DoTheWorkOnTheWholeList(itemList);
}

In other words, it feels like some of your responsibilities may be misplaced - I generally prefer to make services where I can make a single call to them. Then, the asynchronous nature is irrelevant, because you're not performing a sequence of events.

Answer 2

Take a look at Juval Lowy's (author of Programming WCF Services) website for examples of how to achieve asynchronous programming in WCF. The downloads are free; you just have to provide your email address.