Environmental Awareness: Accessing Operating System Information, Special Folders, and More with Visual Basic 6 and the .NET Framework
Swigart Consulting LLC
Visual Basic 6
Summary: This article explains how you can use Visual Basic 6 with the .NET Framework to access user and operating system information that normally would require Win32 API calls. (8 printed pages)
Click here to download the code sample for this article.
There's a lot of user and operating system information that's typically been difficult to get to from Visual Basic 6; however, with a few trivial calls into the .NET Framework, this information is easy to retrieve.
Figure 1 illustrates the retrieval of user and operating system information from Visual Basic 6 with the .NET Framework.
Figure 1. Retrieving user and operating system information
You can see that this application retrieves the domain name, user name, and machine name. It also retrieves the string for the operating system version, letting you know what OS your code is running on. The logical drives are enumerated, and the IP addresses assigned to this machine are also listed—in this case, showing the physical and wireless IP addresses.
In addition, the application is able to retrieve the location for any of the special folders, which include:
To do this with 100% Visual Basic 6 would have required a lot of calls into the Win32 API, and all the goo that Win32 API calls entail. You would have to correctly create your Declare statements, craft structures that match what the API functions need, create buffers to hold strings, and so on. Not to mention that there are a number of API functions that do similar things, some of which are available on one operating system, but not others.
The .NET Framework Class Library (FCL) organizes access to much of this system information under the System.Enviornment class. Tables 1 and 2 present a quick overview of this class, showing that it can provide a lot of information about the machine, user, and application environment.
Table 1. System.Environment properties
|System.Environment Property||Description||Visual Basic 6 Equivalent|
|CommandLine||Gets the command line for this process.||Command function|
|CurrentDirectory||Gets and sets the fully qualified path of the current directory—that is, the directory from which this process starts.||App.Path|
|ExitCode||Gets or sets the exit code of the process.||No equivalent|
|HasShutdownStarted||Indicates whether the common language runtime is shutting down, or whether the current application domain is unloading.||Win32 API|
|MachineName||Gets the NetBIOS name of this local computer.||Win32 API|
|NewLine||Gets the newline string defined for this environment.||No equivalent|
|OSVersion||Gets an OperatingSystem object that contains the current platform identifier and version number.||Win32 API|
|StackTrace||Gets current stack trace information.||No equivalent|
|SystemDirectory||Gets the fully qualified path of the system directory.||Win32 API|
|TickCount||Gets the number of milliseconds that have elapsed since the system started.||Win32 API|
|UserDomainName||Gets the network domain name associated with the current user.||Win32 API|
|UserInteractive||Gets a value indicating whether the current process is running in user interactive mode.||Win32 API|
|UserName||Gets the user name of the person who started the current thread.||Win32 API|
|Version||Gets a Version object that describes the major, minor, build, and revision numbers of the common language runtime.||Win32 API|
|WorkingSet||Gets the amount of physical memory mapped to the process context.||Win32 API|
Table 2. System.Environment methods
|System.Environment Method||Description||Visual Basic 6 Equivalent|
|Exit||Terminates this process and gives the underlying operating system the specified exit code.||End or Win32 API|
|ExpandEnvironmentVariables||Replaces the name of each environment variable embedded in the specified string with the string equivalent of the value of the variable, and then returns the resulting string.||Environ function and custom code|
|GetCommandLineArgs||Returns a string array containing the command-line arguments for the current process.||Command function|
|GetEnvironmentVariable||Returns the value of the specified environment variable.||Environ function|
|GetEnvironmentVariables||Returns all environment variables and their values.||Environ function|
|GetFolderPath||Gets the path to the system special folder identified by the specified enumeration.||Win32 API|
|GetLogicalDrives||Returns an array of strings containing the names of the logical drives on the current computer.||Win32 API|
As you can see from Tables 1 and 2, the System.Environment class provides a lot of information that isn't readily accessible from Visual Basic 6. To use the System.Environment class, you can create a simple COM wrapper class in Visual Basic .NET. Once the COM wrapper is created, you can use the System.Environment class from Visual Basic 6, VBA, ASP, VBScript, or any other environment that can use COM objects.
To create a wrapper for the System.Environment class, you can just create a new Class Library project in Visual Studio .NET 2003, and add a COM Class to your project (see Figure 2).
Figure 2. Adding a COM Class to your project
You then simply create functions that call into the System.Environment methods and properties, and return the results (see Listing 1). In many cases, this involves just one line of code.
Listing 1. Returning System.Environment information from Visual Basic .NET
Public Function GetLogicalDrives() As String() Return System.Environment.GetLogicalDrives() End Function Public Function GetMachineName() As String Return System.Environment.MachineName End Function Public Function GetOSVersion() As String Return System.Environment.OSVersion.ToString() End Function Public Function GetDomainName() As String Return System.Environment.UserDomainName() End Function Public Function GetUserName() As String Return System.Environment.UserName End Function
These functions can then be called from Visual Basic 6 to get the information (see Listing 2).
Listing 2. Accessing System.Environment from Visual Basic 6
Set env = New NetFrameworkWrappers.EnvironmentWrapper txtDomainName = env.GetDomainName txtUserName = env.GetUserName txtMachineName = env.GetMachineName txtOsVersion = env.GetOSVersion
To get the directory for special folders, you need to specify which folder you're interested in. .NET provides an enumeration of all the possible folders, and this list can easily be provided to Visual Basic 6 as an array of strings (see Listing 3).
Listing 3. Returning the list of special folders from Visual Basic .NET
Public Function ValidFolderPaths() As String() Return System.Enum.GetNames(GetType(SpecialFolder)) End Function
This returns an array of strings with the identifiers for all the special folders. You can then pass in the ID of the special folder to get its directory location (see Listing 4).
Listing 4. Visual Basic .NET function that returns the directory location for a special folder
Public Function GetFolderPath(ByVal specialName As String) As String Dim sf As SpecialFolder sf = System.Enum.Parse(GetType(SpecialFolder), specialName) Return System.Environment.GetFolderPath(sf) End Function
From Visual Basic 6, you can just call this function, pass in any special folder ID string, and get the location (see Listing 5).
Listing 5. Retrieving a special folder location from Visual Basic 6
Set env = New NetFrameworkWrappers.EnvironmentWrapper txtMyPictures = env.GetFolderPath("MyPictures")
Information about the current system IP addresses isn't actually provided through System.Environment, but to me, it's part of the same theme. For this, I actually use classes in the System.Network namespace (see Listing 6).
Listing 6. Returning IP Addresses from Visual Basic .NET
Public Function GetIpAddresses() As String() Dim h As System.Net.IPHostEntry = _ System.Net.Dns.GetHostEntry(System.Net.Dns.GetHostName) Dim addresses(h.AddressList.Length - 1) As String For i As Integer = 0 To h.AddressList.Length - 1 addresses(i) = h.AddressList(i).ToString() Next Return addresses End Function
This function first gets the host name for the computer using the Dns class. Then, it retrieves the IP addresses for that host name. The information is returned as an array of strings.
As a convenience, I've already created the wrapper class for System.Environment. The code for the wrapper, and the test application illustrated in Figure 1 are ready for you to download and experiment with. To install the COM wrapper, just execute install.bat, which is located in the download zip file. You can then find the Visual Basic 6 application in the VB6 Projects\Environment folder. The full .NET wrapper solution is available in the VB.NET Wrappers folder.
The theme of Visual Basic Fusion is that you can use everything that .NET offers from non-.NET environments such as Visual Basic 6, VBA, ASP, or VBScript. In this article, you've seen how you can access information that normally would have required Win32 API calls, with just a tiny bit of .NET code.
About the Author
Scott Swigart spends his time consulting, authoring, and speaking about emerging and converging technologies. Scott has worked with a wide range of technologies over his career, beginning with Commodore 64 programming at the age of 12, writing hardware diagnostics for UNIX systems in C++, and building Windows desktop and Web applications. Over the years, Scott has worked with component development, XML technologies, .NET, Web services, and other languages, platforms, and paradigms. With this experience, Scott has seen how technology evolves over time, and he is focused on helping organizations get the most out of the technology of today while preparing for the technology of tomorrow. Scott is also a Microsoft MVP, and co-author of numerous books and articles. Scott can be reached at email@example.com.