Microsoft DOS Commands in VBA-2 ~ LEARN MS-ACCESS TIPS AND TRICKS

Sunday, May 6, 2012

Microsoft DOS Commands in VBA-2

Continued from Last Week.

With the MkDir() Command, we were able to create a folder on disk, with the help of a small VBA routine that we wrote last week. We don’t even need a separate program to do this, we can directly execute this command from the Debug Window, like the following example:

MkDir "C:\Developers\Projects"

The only disadvantage of this method is that we cannot perform a validation check before executing this command. In the VBA program, we have included the validation checks. That program uses constant values as Path, and with few modifications, this program can be further improved to accept the Path string as Parameter to the CreateFolder() Function. The Code with improvements is given below:

Creating a Folder.

Public Function CreateFolder(ByVal folderPath As String)

Dim msgtxt As String, folderName As String

'extract the new Folder Name from the folderPath Parameter
folderName = Right(folderPath, Len(folderPath) - InStrRev(folderPath, "\"))

'check for the new folder name, if not found proceed to create it
If Dir(folderPath, vbDirectory) = "" Then 
   msgtxt = "Create new Folder: " & folderPath & vbCr & "Proceed ...?"
   If MsgBox(msgtxt, vbYesNo + vbDefaultButton1 + vbQuestion, "CreateFolder()") = vbNo Then
      Exit Function
   End If
   MkDir folderPath 'try to create the new folder

'check whether the folder creation was successful or not
   If Dir(folderPath, vbDirectory) = folderName Then
      msgtxt = folderPath & vbCr & "Created successfully."
      MsgBox msgtxt
   Else
'if the code execution enters here then something went wrong
      msgtxt = "Something went wrong," & vbCr & "Folder creation was not successful."
      MsgBox msgtxt
   End If
Else
  'the validation check detected the presence of the folder
   msgtxt = folderPath & vbCr & "Already exists."
   MsgBox msgtxt
End If

End Function

In all the above and earlier examples we have provided the full path of the existing location, where we need the new folder to be created, with the new folder name at the end. If you are sure where the current location is (or the active location of the current database on disk) then you can issue the MkDir() command with the new folder name alone, like the following example:

MkDir "Projects"

Finding out the Current Folder.

As far as VBA is concerned the current location is not what you have selected using Windows Explorer. Or the one you have selected using DOS Command ChDir(), runs directly under the DOS Command Prompt.

But, with a small trick we can find out which is the current folder that VBA is aware of, that is by running the Shell() command directly from the Debug Window to invoke the DOS Command Prompt from VBA, like the example given below:

Call Shell("cmd.exe")

The above command will open the DOS Command Prompt (if it is minimized on the taskbar, then click on it to make that window current), and the Cursor will be positioned in the current folder. Check the sample image given below:

If you have used MkDir "Projects" like a command without knowing where it is going to be created, then type Dir and press Enter Key to display a list of files and directory names with the label <Dir> to indicate they are folders.

That doesn’t mean that the above method is the only option to check the Default Database Folder location. Select Access Options from Office Button and select the Popular Option Group(Access2007) and you can see the Default Database Folder settings there. You may change it if you need to change it. Check the image given below:

Try to open a database from some other location on disk, but this setting will not change and the Default Database Folder will remain active as per this setting. Without touching the above Access default setting, we can change the active folder to the newly opened database’s parent directory with the use of the following DOS Commands from VBA (you can try this by typing these commands directly on the Debug Window):

? CurrentProject.Path

This is not DOS Command, but the above VBA statement retrieves the active database's Path. Let us assume that the retrieved location of the current database is: C:\MDBS

Using the above information in the next two DOS Commands we can change the control to the active database's location, without changing the Default Database Path setting, we have seen earlier:

ChDrive "C" 'change control to C: Drive. This is necessary if the control was on a different drive ChDir CurrentProject.Path 'change control to the active database's folder

ChangeDir() Command.

By combining the above statements we can write a very useful Function ChangeDir() to change the control to the current Database Folder. Copy and Paste the following Code into a Standard Module of your Database and save it:

Public Function ChangeDir()
Dim vDrive As String * 1, sysPath As String

'get current database Path
  sysPath = CurrentProject.Path

'extract the drive letter alone
'vDrive Variable is dimensioned to hold only one character
  vDrive = sysPath 

'change control to the Drive
  ChDrive vDrive 

'change current location to the database folder
  ChDir sysPath 

End Function

Call the above Function from an Autoexec macro with the RunCode Action or from the Form_Load() Event Procedure of the first Form open (like the Startup Screen or Main Switchboard) to change control to the active database folder.

LEARN MS-ACCESS TIPS AND TRICKS

Sunday, May 6, 2012