Make your own free website on Tripod.com
         

     Scripting with Visual Basic

   When programming in Windows (R) environment, scripting might come in quite handy. Usually scripting is accomplished through writing vbscript, jscript or wscript program files that contain the instructions needed to be executed by script engine. Once a script file is dubugged and saved it can be executed. You, as a Visual Basic programmer can use the power of scripting from your own Visual Basic applications. One area where scripting can come in very handy is file manipulations. I will show you how you can move and delete files using Microsoft (R) Scripting runtime from Visual Basic.

First of all, to be able to use scripting runtime you have to add a reference to it. To do that, start the application that will use the runtime. (Start a new project if you want just to try runtime first). Once the project is loaded, go to Project menu and click on References... . A references dialog box should appear. Find "Microsoft Scripting Runtime" and click on it. Press OK. The reference to runtime has been added. Now to our example.

Create a file called test.txt and place it in drive c:\. This will be our test file that i will use to demonstrate a one very simple function of scripting runtime. Now, in the Visual Basic project open the main form and add a button and call it cmdCopy. I will add the code to this button so that when pressed it will copy test.txt from c:\ to d:\. Also add another button that will delete the copy you just moved and call it cmdDelete.

When performing any file manipulation with scripting runtime (that's what we are going to do) you need an instance of FileSystemObject. In my example, I declared a private variable called fso of type FileSystemObject to get that instance:

Private fso As Scripting.FileSystemObject

Private Sub Form_Load()

    Set fso = New FileSystemObject ' creates an instance of FileSystemObject
 
End Sub

Don't forget to unload the instance to prevent memory leaks:

Private Sub Form_Unload(Cancel As Integer)

    If fso Is Nothing Then ' if FileSystemObject was not loaded
        Exit Sub      ' then exit
    Else              'otherwise
        Set fso = Nothing ' unload FileSystemObject
    End If

End Sub
 
Once the loading and unloading of fso is taken care of, look at the code for copying the c:/test.txt to d:\.

Private Sub cmdCopy_Click()

    fso.CopyFile "c:\test.txt", "d:\copyOftest.txt"  ' perform copying

    If fso.FileExists("d:\copyOftest.txt") Then  ' check if it was copied
        MsgBox "File was successfuly copied!", vbInformation, "OK"
    Else
        MsgBox "Copying failed", vbCritical, "Error"
    End If

End Sub
 
That's all what it takes! Notice that when copying the file, you need to specify not only the new location but also the new filename for the file being copied (the old name can be used as well as the new one). Also notice the If-Else-EndIf block for checking if copy operation was performed.

To delete just newly copied file, code cmdDelete button:

Private Sub cmdDelete_Click()

    fso.DeleteFile "d:\copyOftest.txt", True   ' try to delete

    If fso.FileExists("d:\copyOftest.txt") Then  ' check if deleted
        MsgBox "Deleting failed", vbCritical, "Error"
    Else
        MsgBox "File was successfuly deleted!", vbInformation, "OK"
    End If

End Sub

Copying files is not the only operation you can perform with FileSystemObject. There is so much more functionality to explore. To obtain complete list of functions you can use with Scripting Runtime press F2 while in Visual Basic to get Object Browser and browse through Scripting library. To prove to you that there is much more to scripting power than just plain file copying, let's expand our current application to show the information of a "c" drive on your machine (or which ever drive you wish). Add another command button and name it cmdDrives. Also add expanded text box and name it txtDrive. Make sure that the Multiline property of txtDrive is set to True. After you added the controls, here is the code that when the cmdDrives is pressed outputs the drive letter, file system, drive type and free space of the drive in txtDrive text box:

Private Sub cmdDrives_Click()

    Dim strText As String

    strText = strText + " Drive letter: " & fso.drives("c").DriveLetter & vbCrLf _
    & " File System: " & fso.drives("c").FileSystem & vbCrLf _
    & " Drive Type: " & fso.drives("c").DriveType & vbCrLf _
    & " Free Space: " & fso.drives("c").FreeSpace & " bytes"

    txtDrive.Text = strText
End Sub
 
As you can see from the code it was very easy to obtain the information. We could have done this using API calls. And it is your call which way you want to program. If you are inexperienced in Windows API functions, use scripting runtime. Otherwise API calls might be better not for performance reasons but for the fact that API calls need only function declarations and no library references.

That is all for this topic. If you have any questions please email me. To download the example, click here

Topics - Home

Made By Laimonas Simutis. 2001. laijerrad@yahoo.com