Faster code, faster forms
This column appeared in the September 1998 edition of
EXE, and was a review of the newly-available Visual Basic 6.
The version 5 release of Visual Basic delivered a few
fundamental changes. The new Integrated Development Environment was the most
obvious, while the "true" compiler was one of the features that was
hitherto the most asked for. There was also direct support for Internet
development. To reinforce the strength of the product, the Enterprise Edition
also shipped with SQL Server and Transaction Server. These new features gave
the product specification quite a leap from version 4.
Version 6 of the product is more of a maturation of the
previous release. In this month's column I shall be discussing the new features
to be found in the product. This review is based upon release candidate 1 of
Visual Studio 6 Enterprise Edition, so while I wouldn't expect any
specification changes to creep in at this late stage, you never know what they
might drop or throw in at the last minute.
My first observation is that the Visual Studio 6 product is
much more of an integrated effort than has previously been the case. After the
installation you will find that Visual Studio 6 is now under a single menu
group on the Start menu, with one menu entry for each specific language
product. Everything else is bundled under a common Tools submenu and, if
appropriate, an Enterprise Tools submenu. Because the pre-release software
(that I saw) only appeared in the full Visual Studio format I cannot tell how
the standalone Visual Basic product will be packaged. However, it's quite
apparent that Microsoft will be making a stronger-than-ever effort to get you
to buy the full Visual Studio package. The splash screen that is displayed when
the IDE loads has been updated to emphasise the fact that it's part of the
Visual Studio family. There is also a healthy complement of BackOffice products
for the developer to work with.
Despite the many new features one thing that still hasn't
changed is the menu editor - it's still the same as in version 1! While the
menus that it produces are completely usable it is not possible to directly
create Office-style menus. Apparently Microsoft are not prepared to make the
relevant libraries redistributable so it's necessary to resort to third party
tools to achieve this effect. In next month's column I'll be giving some
coverage to this very issue.
General features
Microsoft has, as usual, been promising faster code, faster
forms, and even faster natively compiled apps in Visual Basic, and this does
appear to be the case. The native code compiler is still the Visual C++
back-end, which itself is currently getting very favourable reviews - even in
its beta state - for its performance increases (to the order of a 20%
improvement in speed). Performance has also been refined for multi-processor
targets.
This new version contains additional string manipulation
functions that are really intended for grown-ups. The StrConv function has a
new optional parameter that allows you to specify a LocaleID if you don't want
to use the default one. A new Filter function returns a subset of a string
based upon a filtering criterion. There are also functions to reverse, join,
and replace strings, new formatting functions, and a couple of routines that
give you the names of a weekday or a month that are derived from a date.
One feature that I really do like is the FileSystemObject that
comes with all editions of the product. This option needs to be checked in the
References dialog box under the Project menu - it's called the Microsoft
Scripting Runtime. Once you've created a new instance of one of these objects
you can do all sorts of useful things with folder and file objects, such as
create and delete them, and get information about them. For example if you want
to be able to delete a folder and not have to worry about writing the logic to
traverse the entire subtree and delete everything else first then you can use
the DeleteFolder method. To test this I created a directory called c:\Test and
then copied the contents of the nearest data CD into it. Because it was a CD
all of the files were marked as read only. I ran the following
Dim fso As New FileSystemObject
Fso.DeleteFolder "c:\test", True
Set fso = Nothing
and it worked perfectly (the True parameter is to tell it to
ignore any read-only flags).
The manipulation of controls has been improved somewhat. Many
of the standard controls now have a Validate event that offers a better degree
of control than the LostFocus event. If you set the corresponding
CausesValidation property to True then the Validation event is fired when the
user attempts to exit the control. The LostFocus event is only fired once the
validation has been successful. You can also programmatically add and remove
controls to or from a form at runtime.
One feature that was sorely missing from version 5 has now
been addressed: namely, user-defined types can be arguments or return types of
public properties and methods. Similarly, Functions and property procedures can
now return arrays.
I was slightly surprised to find that Visual Studio 6 still
displays the Help Workshop in the Tools menu. The newer HTML Help has been in
circulation for a little while now and Microsoft has stated that it is the way
forward in terms of help technology. However the HTML Help Workshop is on disk
1 so at least it's catered for, it's just not displayed in the Setup program.
For new systems I would suggest that it's worth trying to make the effort to
get to grips with the new help system if only to keep your skills marketable.
The Application Setup Wizard has been enhanced and updated to
become the Package and Deployment Wizard. The approach remains the same - you
either want to create a Setup program or an Internet deployment pack. However
the files that go to make up the installation pack are now placed in a CAB file
as found in Microsoft's commercially available products. One useful addition to
the Wizard is that you get an editable mini-explorer view of the menu entry
that will be created for the Start menu, so you can configure this accordingly.
The backdrop of the resultant setup program is still the gradated blue to black
which to me feels old hat now, but overall the Wizard is a useful and
worthwhile product. I think that professional developers will still want to
turn to a third-party tool (such as InstallShield) for their installation
routines.
Database and BackOffice
This is perhaps the area where the greatest improvements have
been made. As has already been widely reported Visual Basic 6 now comes with
ADO (ActiveX Data Objects). ADO is the next logical successor to both DAO and
RDO although both of these technologies are still present and supported. The
strength of ADO is that it provides a common programming model for both local
and remote data access. This comes about because it's actually an object
wrapper around OLE DB, an architecture that exposes a set of COM interfaces to
provide uniform access to data stored in diverse information sources. These
sources could be hardware devices, conventional relational databases, or they
could be a rich source of data such as an Exchange Server, the forthcoming NT5
directory services, or indeed in some future source of data that has not been
invented yet. The point is that it helps to provide a common method of
accessing data wherever it is. Many corporate systems that are developed today
often have to import data from different sources, often to a central location
to simplify the design. With an OLE DB platform you should be able to access
multiple diverse data sources from different locations in a tidy and consistent
manner.
Several new and enhanced tools beef up the data access side of
the product. The Data Environment Designer is an ADO replacement for the
UserConnection designer (which is still included). It's purpose is to provide a
design time environment that lets you create a data access definition that can
be programmatically manipulated at runtime. It provides support for the
creation of multiple ADO Connection and Command objects within one
DataEnvironment object, thereby supporting connections to multiple data
sources.
The Data Report Designer provides the ability to create banded
hierarchical reports. Fields can be dragged from a Data Environment Designer
and dropped into the report design. When a field is dropped a text box control
will automatically be created that is bound to the relevant DataMember and
DataField properties. Needless to say the Designer has the facility to publish
reports in HTML format as well as directly to the printer. If you choose to use
the print option then you can also generate a print preview window beforehand,
although this can only work if there is a printer driver already installed
because the report engine needs to be able to reference a set of metrics.
Thanks to the careful design that has gone into ADO it is
possible to pass RecordSet objects across process and machine boundaries, which
is most likely to be used in passing data from one tier of functionality to
another. This RecordSet object exists within the full ADO library, but can also
be found as a separate component (set the client to reference the Microsoft
ActiveX Data Objects RecordSet 2.0 Library). The benefit of also providing a
separate implementation is that much of the associated baggage can be
discarded. Because the passed object is purely a RecordSet there are no
Command, Connection, and Parameter objects and therefore the footprint is as
unobtrusive as possible.
Integration with Microsoft Transaction Server (version 2) has
been tightened, and there is support for the Microsoft Message Queue
technology.
Internet
Although Internet technologies still continue to be
implemented ad nauseum throughout everything that Microsoft produces, there are
in fact two specific new related features worthy of note here. The first is
that a new icon labelled IIS Application is visible in the New Project dialog
when Visual Basic 6 is loaded. IIS Applications offer new elements called
WebClasses which are units of code that can be run from an Internet server. A
WebClass is created with Visual Basic and compiled into a DLL. The DLL is
launched at runtime by an Active Server Page (ASP) instance, and the WebClass
and the ASP exist in a 1 to 1 relationship for the duration of a single
client's connection. WebClasses have been developed by Microsoft to help
developers who aren't familiar with HTML to get up and running with Internet
server applications. Using Visual Basic as the underlying language lets the
developer interface directly with the IIS object model and hence be given the
opportunity to write very efficient code. The WebClass, for its part, generates
an appropriate stream of HTML derived from the underlying Visual Basic code.
The second item of note is the DHTML Designer. DHTML is still
in the process of being agreed upon by the Internet community as a whole, but
Microsoft implemented it anyway in Internet Explorer 4. A DHTML based
application is created through another new icon in the New Project dialog. Once
in the design window a page can be created from scratch, or an existing page
can be referenced and modified. DHTML allows you to write Visual Basic code
that will result in a local response to user activity on a web page, without
the need to pass the information back up to the server for processing.
Documentation
Further evidence of the integration with Visual Studio can be
seen in the disappearance of the Books Online application. All of the
documentation for each development tool has now been assimilated into the MSDN
library. Microsoft Press has announced for September the Visual Basic 6
Reference Library (ISBN 1-57231-864-3) which appears to come as three manuals,
and the Visual Basic 6 Programmers Guide (ISBN 1-57231-863-5). Microsoft has
also confirmed that they will be producing a Visual Basic 6 title in the
Mastering Series.
The Visual Studio 6 product set is due
for release on September 2nd 1998 although at the time of writing
the pricing had yet to be announced. Visual Basic 6 will come
in Learning, Professional and Enterprise editions.
