How to Determine if a Program Is Running as a DLL or an EXE

• Enterprise Edition of Microsoft Visual Basic, 32-bit only, for Windows, version 4.0

SUMMARY

This article describes how to determine whether the Enterprise Edition of Microsoft Visual Basic, which creates DLL or EXE files, 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

   EXE=1

   EXE=0

Method 3 - Use the Windows API to dynamically determine the file extension

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.