Richard Thomason: TechEd 2008 Day 2

3 Oslo, Dublin and WF4 - David Chappell

Not the ex-Compsoft employee David Chappell, instead a rather annoying "gee dub-f" Seattle microsoftie.

This session promised a rewrite of the Workflow foundation. I went to a couple of sessions on WF3 last year and Tim investigated it for Hippo, and both of us found it to be inadequate. The hope is that the new version may be more up to scratch.

As it turns out, there has been a lot of work done. The workflow engine got a rewrite and is "much faster". They added a Flowchart model in addition to the Sequential and StateMachine ones. To help people who are afraid to write their own host process (?) sic, Dublin provides something like a service host for WF activities, including start/stop/restart and persistence. WF is the sort of thing you would use with SharePoint to implement simple activities beyond the scope of form-filling. Comparisons with Biztalk are probably not useful. Biztalk is not free.

Latterly, David spoke about Oslo, which is a general purpose modelling platform; here's an url for you to look at:

Unfortunately, my BLX detector was activated during this part of the talk, and when he started talking about modelling schema languages and first releases, it triggered the "bail out now before the Tourette's kicks in" alarm.

4 Developing data centric web applications - Jonathan Carter

This session demonstrated substituting DynamicData controls for normally bound ones using templates to reduce the amount of code in asp forms. I can't resist saying that these are features that have been in Equinox since version 1 :) but enough of that since we didn't do forms in the web server, yet. There is a large amount of work to set up the template and refer to it in the form, however it is work that needs doing only once, and is extensible with user-defined types and so on. This does look good, especially for new, more substantial applications, but it still gives me the "whole load of legwork" feeling, and I don't see the point of reverse engineering it into existing apps. Maybe my expectations are too high.

5 Developing accessible web apps with Silverlight- Sean Hayes

Well it was either this or Windows for Washing Machines. I was concerned to see that the "with Silverlight" part of the title was missing from the title slide, but I thought I'd stick it out to see what I could learn. Sean rehearsed the well-known accessibility feaures in standard HTML - alt text and so forth, then went on to describe ARIA, which extends accessibility features in the latest browsers now, and will be part of HTML 5. It provides assistance in more complex controls such as drop-down lists and slider controls, etc, as well as a "live region" feature that allows assistive technology to handle dynamically updating areas of the screen.

Silverlight 2.0 is fully enabled for accessibility, and in this repect is unlike most modern browser-based implementations. Audio have have transcripts, and video can have captions or subtitles, as well or instead of transacripts. Finally you can use descriptions, which can pause the video if necessary. PC media allows for sign language translation more easily, since unlike TV it can be switched off and on.

6 LINQ and C# - Luke Hoban

This session is a warm-up for tomorrow's dead exciting LINQ to Anything talk, to remind me of the deep details of LINQ in C#.

LINQ works with both objects (via an enumerator interface) and via SQL (via a query interface). It's the same deal for both, and only varies in the provider and the references, eg Customer object versus db.Customer data provider, and so on. Luke showed a simple example querying customers:

var query = from c in LoadCustomers() where == "London" select c;
var query = LoadCustomers().where(c => == "London");

He demonstrated the .Net Reflector tool which shows details of generated code. CachedAnonymousDelegates turn lambdas into references to private static methods. If static methods start with "this", it defines an extension method that can be used with dot notation. He then overrode the Where method ("yield return" adds item into the output collection) on IEnumerable, which only executes as much as it needs to get to the next element, then returns that.

He then showed a SQL version demonstrating expression trees, which showed how out of memory execution works. Lambda expressions can also be turned into expression trees:

Expression<Func<Customer, bool>> MyExpr = c => c.City == "London";

IQueryable is equivalent to IEnumerable for out of memory types. It contains a pointer to an expression tree, and a Provider which can executes the query. The Provider needs to traverse the expression tree and provide results for resolvable items.

7 Using multicore resources with the concurrency runtime - Joe Duffy

Anything that makes it easier to do multi-thread programming is worth checking out. This was a brain melting discussion of how Windows native and the CLR do thread pooling and task allocation. There are two separate systems which mirror each other. The Concurrency runtime will ship with VS 2010.

The CTO of Intel said last February that he believes we'll have 80 cores in our pc's within the next decade. Secondly although Moore's law is not broken for numbers of transistors available, the fact is that the increase is not going to lead to an increase in speed as it has done in the past, so therefore in order to speed things up we will need to be looking at more concurrency.

The main technique of interest Joe discussed was task stealing, which gives much better performance in highly parallelised processes where threads create tasks recursively. The way it works is that threads can push and pop tasks on their local FIFO queue without locking (except the first one), and if other threads run out of work, rather than wait idly they can lock and pop other queues on a LIFO basis, thus maximising throughput.