2007-02-07

ECO book at last!

Hi all

I have finally reached a point where I can dedicate a few hours each today to "something new" and have decided that the ECO book I have always wanted to write would be great fun. My first idea is to create 2 or 3 separate items:

Title: ECO jump start
This would be in paper / PDF format and would contain a set of exercises for a new user to follow in order to get started with ECO as quickly as possible. It would basically cover creating a simple model, prototyping using auto-forms, using the different handles, databinding, parent-child grids, creating/evolving the DB, OCL / code derived / reverse derived attributes, and stuff like that.

Title: ECO API
This would be an electronic format which would basically be a "Press F1" reference.

Title: ECO book
This would either be a paper/pdf format or, if possible, part of the ECO API document. It would be a technical overview of the framework + its services and abilities. I imagine it might be similar to my ECO Services chapter, except I'd probably include a set of "How to" items at the end of each chapter.


The plan here is that we get

1: An easy way for people to assess exactly what ECO does, and to quickly start creating simple "test" applications.
2: A complete reference for information on specific items where you would normally find yourself hitting F1.
3: A conceptual overview of the whole thing, explaining how it all works together and how to achieve certain goals.


This is what I have in mind at the moment, but it could all change based on the feedback I get :-) The above is basically the order I learned in when I learned Bold and then later moved over to ECO, it goes from simple through to in-depth. What I want to know is

A: Do you think I should go for 3 separate items or try to combine the last 2?
B: Is there anything I have missed?
C: What information would you like to see?

As a closing note I will paste in a table of contents I wrote 729 days ago when I first decided this would be a good idea if only I had the spare time :-) It's not necessarily what I still have in mind, but it might get some brain cells bubbling in your heads to get us all started off. If there are any topics you guys mention that I have missed I will add them to my list. Due to its age (1 day short of 2 years old) it is based on ECO II, so there are lots of nice new ECO III items I can put in such as creating your own services, state machines etc.


An overview of ECO
What is an ECOSpace
Modeling an application
Attributes, Methods, and Relationships
OCL Derived attributes
Code derived attributes
Reverse derived attributes
Inheritance Vs Composition
Packages
Creating a simple ECO WinForms app
Creating a simple ECO ASP.net app
Creating a simple ECO Webservices app
Borland.ECO namespaces
Handles
ObjectRepresentation
Persistence
Services
Subscription
UmlRt
WinForm
Persistence
Changing persistence
Evolution
Custom persistence mapping - AutoInc etc
Reverse engineering an existing database
OCL



Also need to include multi-user support, optimistic locking, change propagation, reconciliation, object locking regions, writing your own services + OCL extensions.



Thanks for your feedback!


Pete

2007-02-01

ECO extensions 2.1 released

I have just released a minor update to ECO extensions. It contains a fix for a bug that would prevent the DirtyObjectCatcher from catching modified objects for MDI child forms.

string.GetHashCode

I recently developed a simple support application that allows users on a PC to provide a one-off security number to a Pocket PC user and when entered the PPC will perform a specific support function.

I used the same class to generate these security codes in both the desktop and compact framework applications, tested it quite thoroughly and it all seemed to work fine. However once deployed it became evident that the codes provided by our support department were being rejected by the PPC as invalid. So what went wrong?

Seeing as the same class was used for both applications I thought it would be okay to test the encoding/decoding of command numbers on only a single platform, and this was my mistake! The routines use string.GetHashCode() to add a checksum to the end of the security codes just to prevent the user from performing actions without authorisation. For reasons I cannot imagine the implementation of string.GetHashCode() is different in the compact framework from the one in the full .NET framework. It was due to the result of this method being different on the two platforms that the codes were being rejected.

So, I have disassembled the compact framework version and used that in my desktop application instead, and now it works just fine. Here is the code....

public int MyHashCode(string value)
{
int charIndex = 0;
int num1;
int num2 = 0x1505;
int num3 = num2;
char currentChar;
while (charIndex < value.Length)
{
currentChar = value[charIndex];
num1 = (int)currentChar;
num2 = ((num2 << 5) + num2) ^ num1;

if (charIndex == value.Length - 1)
break;

num1 = value[charIndex + 1];
if (num1 == 0)
{
break;
}
num3 = ((num3 << 5) + num3) ^ num1;
charIndex += 2;
}
return (num2 + (num3 * 0x5d588b65));
}

2007-01-19

Testing a website with a root path

This post is really a reminder to myself, so that I can find the information quickly for the next time I reformat my hard drive!

To run a website with a root path in Visual Studio 2005 follow these steps:
  1. Tools->External tools menu
  2. Click Add
  3. Title = Webserver
  4. Command = C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\WebDev.WebServer.EXE
  5. Arguments = /port:8080 /path:$(ProjectDir)
  6. Tick "Use output window"
Whenever you need the webserver running just open your project and go to Tools->Webserver.

2007-01-17

Calling base constructors in C#

I occasionally find it annoying that I cannot specify at which point in a class's constructor I wish to invoke the base constructor. Having C# always invoke it before any of the code in my descendant constructor is executed sometimes causes me problems.

Considering .NET is capable of calling the ancestor constructor at any point I wondered why C# wont allow it. I contacted Anders Hejlsberg and he was kind enough to reply, unfortunately he seems to have answered a question I didn't ask :-)

Anyway, I have been deleting some old emails today and I came across his response, which he gave me permission to publish:

The problem with Delphi's model (allowing constructors to be called on
an already constructed object) is that it makes it impossible to have
provably immutable objects. Immutability is an important concept because
it allows applications to hand objects to an external party without
first copying those objects and still have a guarantee that the objects
won't be modified. If constructors can be called on already constructed
objects it obviously isn't possible to make such guarantees. In Delphi's
case that may be ok since Delphi doesn't really make type safety
guarantees anyway (you can cast any object reference to a
pointer-to-something and start poking away), but .NET goes further with
type safety and this would be a big hole.

There, now get out of my head ;-)

Anders

2007-01-11

SQL Server amazes me!

Well, SQL Server amazes me, but not because I am impressed!

Today I wrote an application that does the following:
01) Find all ZIP files in a specific folder
02) Open each ZIP file in turn
03) Extract an XML file from the ZIP into an array of bytes
04) Insert that data into a table

There are 1,978 files in this folder and the XML within each ZIP file is around 2MB in size.

I ran this app and was really surprised at how soon my PC started to crawl, it was so slow that it was taking over 10 seconds to switch between MSN and a Skype text-chat window. So I decided to monitor the process.....

Importing the zip data into SQL Server took a total of 19 minutes and 15 seconds (this includes unzip time). What concerns me is that SQL Server's RAM usage went up to 830MB at its peak, this is what was crippling my PC. Twenty minutes after my app had finished SqlSevr.exe was still holding over 700MB of RAM, I then restarted my PC. SQL Server was using more RAM than I had available and was forcing my PC to use virtual memory!

So I decided to try FireBird 2.0

Importing the zip data into FB took a total of 15 minutes and 15 seconds (again including unzip time). RAM usage for FB started at 21MB but dropped to 16MB at home point within the first 5 minutes. It's memory consumption remained at 16MB.

In both cases I was creating + committing a transaction around each INSERT command. In fact it was the exact same code, I just did a search + replace from Sql to Fb.

Amazing!

2007-01-02

DaDa

Today my baby girl looked at me, said "DaDa" for the first time ever, and then giggled. What a great day! :-)