Q150211: HOWTO: Determine if a Program Is Running as a DLL or an EXE

Article: Q150211
Product(s): Microsoft Visual Basic for Windows
Version(s): 
Operating System(s): 
Keyword(s): kbGrpDSVB
Last Modified: 11-JAN-2001

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The information in this article applies to:

- Microsoft Visual Basic Learning Edition for Windows, version 6.0 
- Microsoft Visual Basic Professional Edition for Windows, version 6.0 
- Microsoft Visual Basic Enterprise Edition for Windows, version 6.0 
- Microsoft Visual Basic Professional Edition for Windows, version 5.0 
- Microsoft Visual Basic Enterprise Edition for Windows, version 5.0 
- Microsoft Visual Basic Enterprise Edition, 32-bit, for Windows, version 4.0 
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SUMMARY
=======

This article describes how to determine whether Visual Basic is presently
running an EXE or DLL program. This is useful to know if both an EXE and a DLL
version of a program have been created, and different actions need to take place
based on which version is loaded.

MORE INFORMATION
================

There are several ways to determine whether a running program was loaded as an
EXE or DLL.

Method 1 - Place the information in one of the resource stamps
--------------------------------------------------------------

Choose the Options button when making the EXE or DLL. In the Version Information
section, select File Description, and type in the type of file to be compiled.
To test this in the running program, enter the code below to see a MsgBox with
the correct type:

     If App.FileDescription = "EXE" Then
        MsgBox "I am an EXE"
     ElseIf App.FileDescription = "DLL" Then
        MsgBox "I am a DLL"
     End If

Method 2 - Conditional Compilation
----------------------------------

If the version information fields are being used, use Conditional Compilation to
determine if a program is a DLL or an EXE, as in the following code:

     #If EXE Then
        Msgbox "I am an EXE"
     #Else
        MsgBox "I am a DLL"
     #EndIf

Before compiling the EXE, from the Tools menu, select Options, select Advanced
Tab, and type the following in the Conditional Compilation Arguments field:

     EXE=1

If a DLL is being compiled, type the following in the Conditional Compilation
Arguments field:

     EXE=0

In Method 2, code that is not required for a DLL or an EXE is not compiled. This
is significant if a DLL and an EXE version of a program need to behave
differently.

Method 3 - Use the Windows API to dynamically determine the file extension
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If the Instance handle of the program is passed to the GetModuleFileName API
function, the full path is returned to the program. Microsoft Visual Basic
exposes the hInstance as a property of the App object. For example:

1. Start a new project in Visual Basic. Form1 is created by default.

2. In the General Declarations section of Form1, place the following:

        Private Declare Function GetModuleFileName Lib "kernel32" Alias _
        "GetModuleFileNameA" (ByVal hModule As Long, _
        ByVal lpFileName As String, ByVal nSize As Long) As Long

        Option Compare Text

3. In the Click event of Form1, place the following:

        Private Sub Form_Click()
           Dim sFilePath As String * 255
           Dim sVarFilePath As String
           Dim sFileExt As String

           GetModuleFileName App.hInstance, sFilePath, Len(sFilePath)
           'Trim out the trailing characters

           sVarFilePath = Trim(sFilePath)

           'Capture the file extension
           sFileExt = Mid(sVarFilePath, Len(sVarFilePath) - 3, 3)

           'Make the comparison
           If sFileExt = "EXE" Then
              MsgBox "I am an EXE"
           Else
              MsgBox "I am a DLL"
           End If

           End Sub

4. Compile the program as an EXE. Click on the form, and it correctly informs
  the user whether it was loaded as an EXE or a DLL.

Additional query words: kbVBp400 kbVBp500 kbVBp600 kbVBp kbdsd kbDSupport KBWIN32SDK KBAPI

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Keywords          : kbGrpDSVB 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500 kbVBA600 kbVB500 kbVB600 kbVB400Search kbVB400
Issue type        : kbhowto

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