The Wiert Corner – irregular stream of stuff

Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Archive for the ‘Conference Topics’ Category

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Dear fellow programmer. If you aren’t experienced doing multi-threading, please don’t!

Posted by jpluimers on 2012/07/05

Recently I was asked to investigate a performance problem with a certain .NET application.

The first error I got when getting the app to build in Visual Studio 2010, and then run it was like this:

System.ComponentModel.InvalidAsynchronousStateException was caught
  Message=An error occurred invoking the method.  The destination thread no longer exists.
  Source=System.Windows.Forms
  StackTrace:
       at System.Windows.Forms.Control.WaitForWaitHandle(WaitHandle waitHandle)
       at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous)
       at System.Windows.Forms.Control.Invoke(Delegate method, Object[] args)
       at UI.Splash.SetStatus(String status) in C:\...\Splash.cs:line 395
       at UI.Menu.Main() in C:\...\Menu.cs:line 4275
  InnerException:

Someone built their own splash logic with multi-threading.

Funny that today, this got answered on StackOverflow by [WayBack] mgie: [WayBack] multithreading – TMonitor synchronization / Application.ProcessMessages – Stack Overflow.

Though that is a Delphi link (and points to the nice libraries [Archive.is] AsynCalls and [WayBack] OmniThreadLibrary), the most important link it contains is to  [WayBack] Borland Newsgroup Archive :: borland.public.delphi.internet.winsock :: Re: Disconnect TIdHttp in thread.

That sounds like a Delphi link too, but the subtitle “‘Ways to get into avoidable trouble with threads, V1.2′” hints the essence: it is a post that describes in an environment-agnostic way how to avoid multi-threading problems.

Recommended reading!

Anyway: Building multi-threaded code is hard. Even harder fleshing out all the corner cases and potential error conditions.

No matter what kind of programming environment: If you have not done lots of multi-threaded programming, then please don’t do it yourself: go ask someone that does know how to do it. Or better, try to avoid it.

I try to let libraries to the handling of multi-threading for me, if I use multi-threading at all, as others are far better at this than I am.

–jeroen

Posted in .NET, C#, C# 1.0, C# 2.0, C# 3.0, C# 4.0, C# 5.0, Conference Topics, Conferences, Delphi, Development, Event, Java, Software Development, VB.NET, VBS, Visual Studio 2010, Visual Studio and tools, WinForms | 6 Comments »

ISO 8601 Date, Time and DateTime in Delphi (was: Simple example to show DateTime.Now in ISO 8601 format on ideone.com | Online C# Compiler & Debugging Tool)

Posted by jpluimers on 2011/08/18

In the past I wrote about a Simple example to show DateTime.Now in ISO 8601 format on ideone.com | Online C# Compiler & Debugging Tool , using ISO 8601 in batch-files, and how ISO 8601 is used in Google Calendar URLs.

Time to write something about ISO 8601 Date, Time and DateTime and Delphi.

First of all the DateUtils unit contains a bunch of routines (for instance DecodeDateWeek) that understand ISO 8601 week numbers, where:

  • Weeks start at Monday
  • The first week of a year contains (these are equivalent):
    • The first thursday in that year
    • Has at least 4 days in that year
    • Contains the 4th of January

Otherwise the week containing January 1st is week 52 or 53 of the previous year

ISO 8601 also specifies how to format Dates, Times,  DateTimes and durations according to some basic principles.

XML uses ISO 8601 to format Date, Time and DateTime and some other formats as text too.

So it is no wonder that since Delphi 6, it contains a XSBuiltIns unit covering (among other things) ISO 8601 formatting.

Given the many Delphi ISO 8601 relates questions on StackOverflow of which I answered two, and my need for ISO 8601 DateTime conversion for exporting Excel XML, here is are some samples to get started in the unit below (and in this codeplex changeset).

The unit covers Date, Time and DateTime.
You can write similar code for Duration.

Oops, I covered it already in ISO 8601: Delphi way to convert XML date and time to TDateTime and back (via: Stack Overflow)

Read the rest of this entry »

Posted in Conference Topics, Conferences, Delphi, Development, Event, ISO 8601, Power User, Software Development | 4 Comments »

ISO 8601: Delphi way to convert XML date and time to TDateTime and back (via: Stack Overflow)

Posted by jpluimers on 2011/07/19

Recently I needed a way of concerting back and forth ISO 8601 DateTime values used in XML from Delphi.

Thoug the Delphi DateUtils unit has some ISO 8601 features for calculating week numbers, you actually need to the XSBuiltIns unit for converting back and forth to ISO 8601 text representation of a DateTime.

I remembered answering the related In Delphi is there a function to convert XML date and time to TDateTime question on StackOverflow a while ago (and forgot that this was back in 2009 <g>).

ISO 8601 dates can either include a time-zone, or be in UTC, which is not part of that answer. So lets elaborate on that answer a bit now:

UTC times in ISO 8601 format end in a Z time zone designator like this:

    <Created>2011-06-29T17:01:45.505Z</Created>

The Z UTC indicator is basically a shortcut for a timezone offset of +00:00 or -00:00, effectively being a zero (or zulu) timezone.

Nonzero timezones start with an optional + or -, followed by the hours and minutes offset from UTC, for instance +01:00 for the Central European Time zone.

    <Created>2011-06-29T17:01:45.505+01:00</Created>

When you want historical time zones, then you need the Delphi TZDB interface to the historical TZ database.

To do the timezone calculations, I used the TimeZoneBias function from Indy, which is either in the IdGlobal unit (Indy <= version 9) or the IdGlobalProtocols unit (Indy 10 and up).

Conversion is done by using the TXSDateTime (that like all the XS conversion classes descends from TRemotableXS in the InvokeRegistry unit).

Most of the classes descending from TRemotableXS contain two methods: NativeToXS and XSToNative doing the underlying conversions.

Since I didn’t need the historical reference in the TZDB, this is the code that I came up with:

unit Iso8601Unit;

interface

type
  TIso8601 = class(TObject)
  public
    class function DateTimeFromIso8601(const Value: string): TDateTime; static;
    class function UtcDateTimeToIso8601(const Value: TDateTime): string; static;
    class function DateTimeToIso8601(const Value: TDateTime): string; static;
    class function UtcNow: TDateTime; static;
    class function ToUtc(const Value: TDateTime): TDateTime; static;
    class function FromUtc(const Value: TDateTime): TDateTime; static;
  end;

implementation

uses
  IdGlobalProtocols, {IdGlobal for Index   SysUtils,
  XSBuiltIns;

class function TIso8601.DateTimeFromIso8601(const Value: string): TDateTime;
begin
  with TXSDateTime.Create() do
  try
    XSToNative(value); // convert from WideString
    Result := AsDateTime; // convert to TDateTime  finally
  finally
    Free();
  end;
end;

class function TIso8601.UtcDateTimeToIso8601(const Value: TDateTime): string;
begin
  with TXSDateTime.Create() do
  try
    AsUTCDateTime := Value;
    Result := NativeToXS; // convert to WideString
  finally
    Free();
  end;
end;

class function TIso8601.DateTimeToIso8601(const Value: TDateTime): string;
begin
  with TXSDateTime.Create() do
  try
    AsDateTime := Value; // convert from TDateTime
    Result := NativeToXS; // convert to WideString
  finally
    Free();
  end;
end;

class function TIso8601.UtcNow: TDateTime;
begin
  Result := ToUtc(Now);
end;

class function TIso8601.ToUtc(const Value: TDateTime): TDateTime;
var
  Bias: TDateTime;
begin
  Bias := TimeZoneBias;
  Result := Value + TimeZoneBias;
end;

class function TIso8601.FromUtc(const Value: TDateTime): TDateTime;
var
  Bias: TDateTime;
begin
  Bias := TimeZoneBias;
  Result := Value - TimeZoneBias;
end;

end.

–jeroen

via In Delphi is there a function to convert XML date and time to TDateTime – Stack Overflow.

Posted in Conference Topics, Conferences, Delphi, Development, Event, Software Development | 7 Comments »

PowerShell: the 2 most common error messages for starters

Posted by jpluimers on 2010/11/11

I’ve waited for PowerShell to become pretty mature before diving into it:
Version 2 has been out for a year, no service packs have been needed, so time to get into it.

PowerShell code can be stored in scripts.
The convention is to use the .ps1 extension for that (even when running PowerShell 2.0. Lesson learned: don’t put version numbers in file extensions).

Having lots of scripting and programming experience, I was a PowerShell beginner, and similar people usually bump into a few error messages.

Luckily, lots of people have gone through that phase, so there is lots of help on the internet.
So this post is not only to show you about some common things you bump into when starting with PowerShell, but also about the power of the internet as a collective pool of knowledge.

This was the first error message I bumped into:

C:\bin>powershell first-script.ps1
The term ‘first-script.ps1’ is not recognized as a cmdlet, function, operable program, or script file. Verify the term and try again.
At line:1 char:16
+ first-script.ps1 <<<<

A message by mosoto (Marcel J. Ortiz Soto) answered this as one of the first in the search results for “is not recognized as a cmdlet, function, operable program, or script file”.
The reason for this error is that unlike cmd.exe (but similar to unix shells), PowerShell does not include the current working directory (.) in the search path.

Solution: prepend the directory for your script file, in this case by prefixing it with “.\”.

This immediately leads to PowerShell rookie error message 2:

C:\bin>powershell .\first-script.ps1
File C:\bin\first-script.ps1 cannot be loaded because the execution of scripts is disabled on this system. Please see “get-help about_signing” for more details.
At line:1 char:18
+ .\first-script.ps1 <<<<

Even though searching for “cannot be loaded because the execution of scripts is disabled on this system” quickly reveals a few posts describing the cause, the error message gives a hint: get-help about_signing.

Executing this on the command-prompt gets youa lot of help about signing:

c:\bin>PowerShell get-help about_signing

This is the summary:

  • PowerShell scripts can be signed.
  • PowerShell as a global execution policy defaulting to Restricted (see below).
  • By default, PowerShell does not want to run any scripts at all.
  • You can assign these values to the execution policy: Restricted, AllSigned, RemoteSigned and Unrestricted
    (note if not specified, the policy is global, so changing this changes it for your whole system, so better define the scope)

Documentation is at:

If you set the execution policy in all scopes to Undefined and the Group Policy is not set, the default execution policy, Restricted, is effective for all users of the computer.

This is how you ask for the current policy:

C:\bin>powershell Get-ExecutionPolicy

This is how you set the current policy to only require remote scripts to be signed:

C:\bin>powershell Set-ExecutionPolicy RemoteSigned

Now you can run unsigned local scripts.
Beware: if anyone sends you a virus in an unsigned PowerShell script, that can now be executed too!

Hope this helps a few other PowerShell rookies too :-)

–jeroen

Posted in CommandLine, Conference Topics, Conferences, Development, Event, PowerShell, Software Development | 2 Comments »

Delphi: Use TStrings to parse non-standard separated strings, and validate it with DUnit tests

Posted by jpluimers on 2010/09/08

Recently, I was at a client where in a project strings had to be split from:

'FI-150 1U; FI-049-I L=20 MM;LET OP LASVORM'

Into:

  • 'FI-150 1U'
  • 'FI-049-I L=20 MM'
  • 'LET OP LASVORM'

At first sight, this looks simple: Semicolon Separated Values and you are done.
Not so fast Mr Smart Alec: watch the optional spaces!

The best thing for problems like these is to start with an empty implementation that some units tests covering it.
I use DUnit for Delphi unit testing.

Unit testing should go with code coverage, but there are few Delphi code coverage articles.
I’ll get into code coverage later on, as I’m working with two of the code coverage people to get this to work nicely with Delphi 2010.

Mock objects can be a good addition to unit testing too, so in a future article, I will cover using mock objects with Delphi.

Read the rest of this entry »

Posted in Agile, Conference Topics, Conferences, Delphi, Development, DUnit, Event, Software Development, Unit Testing | 8 Comments »

Bookmarklets: empower your webbrowser

Posted by jpluimers on 2010/06/02

Next to Greasemonkey – the script engine that empowers FireFox and Chrome, there is another very powerful way to enhance your browser:
Bookmarklets.

Bookmarklets are like shortcuts, but they don’t point to a static URL: they add action, usually by some JavaScript.

If the bookmarklet returns a string, then the browser will follow that as a URL.
But the since bookmarklet  has access to the current page, it can also perform just a local action.

The cool thing is that most bookmarklets work on almost any popular browser.

These are a few bookmarklets that I use on a regular base, most are from bookmarklets.com: Read the rest of this entry »

Posted in Bookmarklet, Conference Topics, Conferences, Development, Event, Power User, Software Development, Web Browsers, Web Development | Leave a Comment »

Windows 7: new shortcut keys (windows hotkeys and more)

Posted by jpluimers on 2010/05/06

In the past there were already a lot of shortcuts, including a few including the windows key.

SEO Consultants has a good overview of both lists.

Microsoft has the classic list.

Windows 7 introduced quite a few more, which I’ll list below.
Read the rest of this entry »

Posted in Conference Topics, Conferences, Event, Keyboards and Keyboard Shortcuts, Power User | 5 Comments »

C# / Delphi – getting the right parameter and function result order for SOAP

Posted by jpluimers on 2010/01/05

Getting different architectures to talk can be a pain, even when using standards like SOAP.

In this case, the .NET WSDL imports Delphi generated WSDL in a different manner than you’d expect at first sight: when having both an ‘out’ parameter and a function ‘result’, the ‘result’ is not imported well.

But alas: SOAP didn’t accommodate for this situation in the past, and now SOAP now has some additions to solve this.

Bruneau Babet explains this here: [WayBack] SOAP inconsistency? Delphi 2010 (Win32) Server and .NET Client swapping ‘out-parameter’ and ‘result’. – Stack Overflow.

There he explains how to use the parameterOrder attribute, which the Delphi WSDL importer and exporter still do not support.

–jeroen

Posted in .NET, ASP.NET, Conference Topics, Conferences, Delphi, Development, Event, SOAP/WebServices, Software Development | Leave a Comment »

Delphi – for … in on enumerated data types

Posted by jpluimers on 2009/10/27

I like [Wayback/Archive] enumerated type a lot.
The allow you to perfectly describe what the members of such a type actually mean, much more readable than a bunch of integer constants!

Given an enumerated type like TTraphicLightColors

type
  TTraphicLightColors = (Red, Orange, Green);

I always wondered why  – since the for ... in statement was added to the [Wayback/Archive] structured statements part of the Delphi language – it is not possible to use a for … in statement like the this:

</span>
<pre>var
  TraphicLightColor: TTraphicLightColors;
begin
  try
    for TraphicLightColor in TraphicLightColor do
      ShowValueAsTraphicLightColor(Ord(Value));
    // [DCC Error] EnumerationEnumeratorDemoProcedures.dpr(63): E2430 for-in statement cannot operate on collection type 'TTraphicLightColors'
end;

Somehow, for ... in [Wayback/Archive]  expects a collection type.
A request for [WayBack/Archive] the for … in do on enumerated types compiler feature is in QC, but it is closed with reason “Won’t do”.

Back in Delphi 2007, I tried working around this by writing a type implementing the GetEnumerator pattern myself, but got [WayBack/Archive] Internal Errors when compiling anything but the most basic sample.

Until today, where I found how I could get that most basic sample to work!
It is an example on how you could implement this: it is research, so you decide if you find the result practical enough to use yourself.

Read the rest of this entry »

Posted in Conference Topics, Conferences, Delphi, Development, Event, F2084, QC, Software Development | 20 Comments »

Delphi – hardcore debugging the intialization of your app, dlls and packages

Posted by jpluimers on 2009/10/15

Recently we got involved with a client having a large and complex application that (historically) consists of

  1. A main .EXE that loads
  2. Many DLLs
  3. Underlying BPLs

One of the biggest problems is debugging the startup sequence.
Somehow, when the Delphi IDE loads DLLs in the initialization sequences of units, it looses its ability symbol tables.

This article describes a few tips on how to debug those, especially where to put breakpoints.
Read the rest of this entry »

Posted in Conference Topics, Conferences, Debugging, Delphi, Development, Event, Software Development | 3 Comments »

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