Month: March 2005

System.Net

~ chriseyre2000 ~ Leave a comment
System.Net contains the ever useful WebClient class.

This allows code such as:

System.Net.WebClient wc = new System.Net.WebClient();
byte[] myDataBuffer = wc.DownloadData(url);
string download = System.Text.Encoding.ASCII.GetString(myDataBuffer);

This allows the text at a given url to be extracted.
Welcome to your own web spider.

API going AWOL

~ chriseyre2000 ~ Leave a comment
Microsoft in their infinate wisdom have decided to break the Mailslot API in the XP line and above. Mailslots were a great means of communicating between processes running under differing user accounts. Under XP these were made unreliable which renders them unusable.

In addition I have found that certain security API’s are missing on Windows Server 2003 custom builds. What is the point of developing against a fixed plaform if a custom build take away API calls?

Small Languages

~ chriseyre2000 ~ Leave a comment
Given that in .NET it is easy to write your own language these could be used to plug obvious holes in the mainstream languages. For example C# makes a pigs ear of it’s constructors.
The minimal syntax is

C () : base () { }

It is possible to have more code in the base () parameters than in the implementation itself.

You need to redefine any constructors that are required in a descendant class.
This makes the definition of mostly empty classes such as exception hireachies far more work than is actually needed.

Delphi has trivial to implement Exceptions :

type
   EBaseException = class(Exception);

  EMyException = class(EBaseException);

This makes their definition and use so useful.

I am wondering if it is possible to create an Exception Definition Language to ease this issue?
I will Blog about this experiment later.

Missing featues : array over enum

~ chriseyre2000 ~ Leave a comment
This is the first article in the blog comparing Delphi features to C#.
C# is a great language but is missing some incedibly useful features from Delphi.

In Delphi you can declare an enumeration as

TEnumColour = (Red, Green, Blue);

You can then declare an array over that enumeration:

TWaveLength : array[TEnumColour] of integer  = (100,200,300);

This is a very powerful technique for ensuring that an enumeration always has valid data.

I have yet to work out how to do this in C#

Localization and Databases

~ chriseyre2000 ~ Leave a comment
I got caught by another localizaion feature of SQL Server today.
SQL Server is not aware of regional settings.

This can be a real pain. If your machine uses say German regional settings and your database returns 1.01  if you use variant conversion routines (hey I am still using ado – we all can’t be on the bleeding edge) this can arrive as 101

This is not what is wanted. This has brought me to question where in a data access layer should the localization go?

CodeGen

~ chriseyre2000 ~ Leave a comment
Code Generation In .NET

This is an important site for an important topic.

Years ago I was involved on a project that was seriously delayed due to the failure of a CASE tool. The project had all of the design completely modelled – it was just that the CASE tool that was suposed to split out the code did not work and the company making it went under.

Code Generation seems to fulfill the promise that CASE tools had been making at the end of the 80’s. Kathleen Dollards approach is entirely feasable. She uses XSLT to generate code from metadata that is either manually created or extracted from for example a database. This is ideal for the middle tier and data access layers which are typically mechanical.

Monoppix 1.0 Released

~ chriseyre2000 ~ Leave a comment
Monoppix 1.0 has been released.

Monoppix is a linux live CD version of Knoppix that includes a working version of Mono.

Knoppix is the major Live CD for Linux. It allows you to experiment with Linux applications without risk to your current operaing system installation. All you have to do is put the Live CD into the CD drive, set the PC to boot from the CD and reboot.

Knoppix is a must have for any PC user. I have managed to get Knoppix to boot and get online even when my PC’s hard drive had failed.

Mono is an open-source implementation of the .NET Framework. There have been complaints that it is hard to configure Linux to get mono to work. A live CD is the best way to demonstrate a working system (so you can easily find what is missing).

Kylix is dead

~ chriseyre2000 ~ Leave a comment
A couple of weeks ago I attended an introduction to Delphi 2005 seminar.

During the Q & A session questions were asked about the future of Kylix.
A quick summary of the answer is that Kylix is dead.
They have no plans to update the product as yet.

GO is not a Transact-SQL statement

~ chriseyre2000 ~ Leave a comment
This week I tripped over the following in the MSDN library:


GO is not a Transact-SQL statement; it is a command recognized by the osql and isql utilities and SQL Query Analyzer.

This is a bit of a pain.

I work on a three tier application that makes heavy use of stored procedures (600 and growing).
 
I have a set of expect scripts that I use to refresh the stored procedures.
These are great – it puts a gui onto the batch files that actually run osql commands.
This takes away a lot of the support issues involved in having people misstype complex commands.

The only problem is the scripts are slow to run. It can take 5 mins to refresh the lot.
This is not really that big a problem – but I am trying to put together a continuous integration server and it would be good if the database could be rebuilt very quickly.

To advance my C# knowledge I have started an ADO.NET app that reads the same batch files and then executes the stored procedures (one per file).

This is where I found the above problem. OleDBCommand objects don’t understand the GO command. It looks like I am going to have to preprocess the script and replace GO with ;

Regional Settings Issues

~ chriseyre2000 ~ Leave a comment
SQL Server 2000 has some interesting issues regarding it’s use of regional settings.
I had a slight problem with some date conversion issues.

If you wanted to convert a string to a date in transact sql typically you would use:

DECLARE @DATE DATETIME
SET @DATE  = ‘2005-03-15 09:46’

This should be 15th March 2005 etc

Since no default conversion has been specified a sane assumption would be that the machines regional settings would be applied. This is how windows applications are supposed to work.

I developed and tested this code on a standard US-English installation of SQL Server.
I even played with the regional settings and it worked just fine.

A customer installed it on a Spanish langauage version of SQL Server and the code broke.
They tried changing the regional settings to US-English and it still did not work.

SQL Server uses the language of the installation to determine the defaults for date conversion.
This is horrible from a testing perpective. I would need to install foreign language editions of SQL Server to test this – and I still can’t find this documented anywhere!

The solution to this problem is to specifiy the date format explicitly using the third parameter of the convert function:

DECLARE @DATE DATETIME
SET @DATE  = Convert(DATETIME,’2005-03-15 09:46′,121)

The moral of this story is don’t trust any automatic conversion always be specific.