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.
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
My.User object contains a great deal of information about the current user.
IsInRole method is a quick and easy way to determine what permissions to
provide the user.
CheckKeys method sets each of the key-related check boxes by using the Boolean
parameters of the
Keyboard object retrieved through
Private Sub CheckKeys() Me.cbAltKey.Checked = My.Computer.Keyboard.AltKeyDown Me.cbCapsLock.Checked = My.Computer.Keyboard.CapsLock Me.cbCtrlKey.Checked = My.Computer.Keyboard.CtrlKeyDown Me.cbNumLock.Checked = My.Computer.Keyboard.NumLock Me.cbScrollLock.Checked = My.Computer.Keyboard.ScrollLock Me.cbShiftKey.Checked = My.Computer.Keyboard.ShiftKeyDown End Sub
FillFromClipboard method calls
GetText on the
Clipboard object, also available
My.Computer object. The
Clipboard object can be used to place items
onto the clipboard as well, including images and other non-text objects:
Private Sub FillFromClipBoard() Me.txtClipBoard.Text = My.Computer.Clipboard.GetText() End Sub
FillComputerInfomethod uses the
My.Computer.Infoobject to obtain information about memory, the operating system, and the current user, and this information is added to the
Private Sub FillComptuerInfo() Me.lbComputerInfo.Items.Add( "Total memory: " + _ My.Computer.Info.TotalPhysicalMemory.ToString()) Me.lbComputerInfo.Items.Add("Physical memory: " + _ My.Computer.Info.AvailablePhysicalMemory.ToString()) Me.lbComputerInfo.Items.Add("Virtual memory: " + _ My.Computer.Info.AvailableVirtualMemory.ToString()) Me.lbComputerInfo.Items.Add("Machine Name: " + _ My.Computer.Info.MachineName.ToString()) Me.lbComputerInfo.Items.Add("User: " + _ My.Computer.Info.UserName.ToString()) Me.lbComputerInfo.Items.Add("O.S.: " + _ My.Computer.Info.OSFullName.ToString()) End Sub
The Look Again button event handler just calls
to reset the check boxes and the text based on changes since the form was loaded.
In the upper-right-hand corer, you see a text box and two buttons: Set and
Get. These are used to write a string to a key in the registry, and to read
that string from the registry, respectively. The Get button's handler calls the
Registry object obtained through
My.Computer. This method takes three
arguments: the key, the value name, and the default value to return if the key
Private Sub btnGetRegistry_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles btnGetRegistry.Click Me.txtRegistry.Text = My.Computer.Registry.GetValue( _ "HKEY_CURRENT_USER\MyObjectKey", _ "MyObjectValue", _ "No Registry value stored").ToString() End Sub
SetValuemethod on the same object, and the three arguments this time are the key, the name of the value, and the actual text to store.
My.Computer.Registry.SetValue("HKEY_CURRENT_USER\MyObjectKey", _ "MyObjectValue", _ Me.txtRegistry.Text) Me.txtRegistry.Text = String.Empty
The second line of code clears the text box when the text is written to the registry.
An event handler is created for both the
Click event on the Play button and
for a double-click event on the
lbClips list box.
Private Sub Play_Event(ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles btnPlay.Click, lbClips.DoubleClick
The job of this event holder is to find the currently selected .wav file and
to play it. This is done using the
Play method of the
Audio object obtained
Finally (and this is about the only tricky bit in this entire example), you
ConnectedToNetwork check box to be updated if you unplug your network
cable. To accomplish this, you need to implement a handler for the
event. To do so, return to the solution explorer and click the Show All Files
button. It turns out that your application includes a hidden file, named MyEvents.vb,
as shown in Figure 3.
Open that file and click on the drop-down menu to show the events. Click on the
NetworkAvailabilityChanged event and the outline of the event handler is created
for you, as shown in Figure 4.
Within that handler, just add a call to
FrmMy.IsNetworked() so that when the
network availability changes (and the event is fired) you can update your check
My object has made creating this application almost absurdly easy. Each
My object objects has many more properties and methods than are shown here,
but they are easy to explore through Intellisense and the MSDN documentation,
now that you know they exist and have seen how they are used.
VB 2 has taken a dramatic lead in Rapid Application Development with the
object. This raises the question of why this facility is not available in C#.
Unless there is a clear performance penalty in using the
My object (I've not
tested that yet) there is no reason to turn our C# noses up at anything that
makes programming easier; after all, the more that is provided by the framework,
the more we can concentrate on designing and building the application.
The example code for this article is available for download.
Jesse Liberty is a senior program manager for Microsoft Silverlight where he is responsible for the creation of tutorials, videos and other content to facilitate the learning and use of Silverlight. Jesse is well known in the industry in part because of his many bestselling books, including O'Reilly Media's Programming .NET 3.5, Programming C# 3.0, Learning ASP.NET with AJAX and the soon to be published Programming Silverlight.
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