Rapid Application Development with VB.NET 2.0by Jesse Liberty
For a couple of years now, I've been touting the Microsoft-endorsed sentiment that it really doesn't matter if you program in C# or in VB.NET, since both are just syntactic sugar layered on top of MSIL (Microsoft Intermediate Language, the true language of .NET). That appears to be changing a bit with Whidbey.
Microsoft seems to be targeting Visual Basic 2.0 a bit more towards Rapid Application
Development (RAD), and thus the designers of VB2 have added a few features to
make developing applications quicker and easier. A key feature in this approach
My object. The
My object exposes six top-level objects for fast
access to various aspects of your application, environment and resources. These
Each of these objects provides extensive properties for access to otherwise
difficult-to-find or difficult-to-manipulate aspects of your running application
and its environment. To see the
My object at work, and to demonstrate
how quickly it allows you to put together an application, I've created a small
test app, shown in Figure 1.
Notice that the application indicates whether or not you are currently connected to the network (this is updated by an event if you disconnect or reconnect), whether or not you are an administrator on this machine, which special keys are depressed, and what is currently on the clipboard. The Look Again button reexamines the keys and the clipboard (there is no event handling for when keys are depressed in this implementation). There are also buttons to get or set a specific registry entry, and there is a list box with information about the computer and the current user. Finally, there is a list of .wav files from the Windows\Media directory, and a button that allows you to play each of these sounds (double-clicking on an entry will play it, as well).
Creating this application took about an hour. It would have gone faster, but
I was learning more about the
My object as I went. By any standard, that is
fairly rapid application development.
You can download the code for this application, but it is quite easy to create it for yourself. (Note: the code was created with the Beta 1 version of Visual Studio .NET 2005.)
To create this application yourself, begin by creating a new VB Windows Application. Drag the list boxes, check boxes, and so forth onto the form as shown in Figure 1. For convenience, name them as shown in Figure 2.
Loading the Form
When the form loads, you'll set the current working directory to C:\Windows\Media
and you'll set the data source for
lbClips to the list of files in that directory
that end in .wav. You accomplish all of this with two lines of code added to
FrmMy_Load event handler:
The first line of code will set the current directory, using
Private Sub FrmMy_Load(ByVal sender As Object, _ ByVal e As System.EventArgs) _ Handles Me.Load
My.Computer.FileSystem.CurrentDirectory = "C:\Windows\Media"
Let's examine this line a bit more closely. The
My object exposes the
object, which provides properties for manipulating the components of the computer,
including the clock, keyboard, file system, and audio. We'll come back to this
object a lot.
My.Computer has a property,
FileSystem, that returns the
object, which in turn has properties and methods for working with drives and
files. One such property,
CurrentDirectory, sets or gets the current directory
for the application.
The second line of code in the
FrmMy_Load method sets the data source for the
list box to the list of files in the current directory.
lbClips.DataSource = _ My.Computer.FileSystem.GetFiles( _ My.Computer.FileSystem.CurrentDirectory, _ False, _ "*.wav")
My.Computer.FileSystem.GetFiles method is being called. It takes
three arguments (in this overloaded version): a directory, a Boolean indicating
whether to recurse into the subdirectories, and a string indicating the wildcards
to use in retrieving the files.
Hey! Presto! the list box is loaded with all of the .wav files from the Windows/Media directory.
The load event handler then calls five other methods as follows:
IsNetworked, to test whether you are currently attached to a network.
IsAdministrator, to test whether the current user is in the Administrators group.
CheckKeys, to set the check boxes for which special keys are depressed (and to try to cheer them up!).
FillFromClipBoard, to fill the text box with the current contents of the clipboard.
FillComputerInfo, to fill the list box with information about the current computer and user.
Each of these methods is made absurdly simple by the
Public Sub IsNetworked() Me.cbNetworked.Checked = My.Computer.Network.IsAvailable End Sub
Network object, available as a property of
My.Computer, has a property named
that returns true if the computer is currently connected to the network. That
Boolean value is used to set the
Checked property of the
cbNetworked check box.
Later in this article, I'll show you how to update that check box by responding
IsAdministrator method is equally straightforward.
Private Sub IsAdministrator() Me.cbAdministrator.Checked = _ My.User.IsInRole("Administrators") End Sub
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