How To Tell Whether an App Runs in VB Design Environment

This article describes how a Visual Basic application can determine whether it is running in the design environment or as an executable file. Two ways that Visual Basic does this are explained.

Visual Basic provides the APP object, which has the property EXENAME. APP.EXENAME reports the name of the executable file when it runs as an executable file. However, in the design environment, APP.EXENAME reports the name of the project. If you use different names for the project and the executable file, then you can use APP.EXENAME to determine whether an application is running in the Visual Basic design environment or as an executable file.

You can also use the Windows API to determine whether an application is running in the Visual Basic Design Environment or as an executable file. When running in the design environment, the application's module name is "VB." However, as an executable file the module name matches the executable file name that is chosen when compiling the application to an executable file from Visual Basic.

Example

You can determine the module name by using the functions GetCurrentTask() and TaskFindHandle() from the Windows API. The following example illustrates how to use the functions to determine whether the application is running in the Visual Basic design environment:

1. Start a new project (Form1 is created by default).
2. Add a new module to the program (MODULE1.BAS by default).
3. Place the following code in the module:

         Type TASKENTRY
            dwSize As Long
            hTask As Integer
            hTaskParent As Integer
            hInst As Integer
            hModule As Integer
            wSS As Integer
            wSP As Integer
            wStackTop As Integer
            wStackMinimum As Integer
            wStackBottom As Integer
            wcEvents As Integer
            hQueue As Integer
            szModule As String * 10
            wPSPOffset As Integer
            hNext As Integer
         End Type
   
         ' The following declare must be entered on a single line
   
         Declare Function TaskFindHandle Lib "Toolhelp" (lpte As TASKENTRY,
            ByVal hTask As Integer) As Integer
         Declare Function GetCurrentTask Lib "Kernel" () As Integer
   
         Function VBDesignEnvironment () As Integer
            Dim TE As TASKENTRY
            Dim ModuleName As String
            Dim hTask As Integer
            Dim r
   
            hTask = GetCurrentTask()
            TE.dwSize = Len(TE)
            r = TaskFindHandle(TE, hTask)
            ModuleName = Left(TE.szModule, InStr(TE.szModule, Chr(0)) - 1)
   
            If ModuleName = "VB" Then
               VBDesignEnvironment = True
            Else
               VBDesignEnvironment = False
            End If
         End Function
   
   						

4. Add the following code to the load event of the form:

         Sub Form_Load ()
            Me.Show
            If VBDesignEnvironment() Then
               Print "Design Environment"
            Else
               Print "Executable"
            End If
         End Sub
   
   						

5. Save the project.
6. Run the application in the design environment. The form should display "Design Environment".
7. Make an executable file from the project.
8. Run the executable file from File Manager. The form should display "Executable".

Notes

• The function TaskFindHandle() is in the TOOLHELP.DLL file. This dynamic- link library does not come with Windows version 3.0.
• You may want to add code to the VBDesignEnvironment() function that checks for errors when returning from GetCurrentTask() and TaskFindHandle().