How To Determine if a Previous Instance of an eVB Application Is Being Run (258088)

SUMMARY

The PrevInstance method of the App object is not supported in eMbedded Visual Basic (eVB) at this time. The CreateMutex API function call can be used to ensure that only a single instance of an eVB application is running on a Windows CE-based device.

MORE INFORMATION

Step-by-Step Example

The code in this example illustrates the use of CreateMutex.

Create a new Windows CE project in eMbedded Visual Basic. Form1 is created by default.

Paste the following code into Form1:

Option Explicit
Const ERROR_ALREADY_EXISTS = 183

Public Declare Function CreateMutex Lib "Coredll" Alias "CreateMutexW" _
   (lpMutexAttributes As Long, _
   ByVal bInitialOwner As Long, _
   ByVal lpName As String) As Long

Public Declare Function GetLastError Lib "Coredll" () As Long

Private Sub Form_Load()

 Dim error_code

 CreateMutex CLng(0), 1, App.Title
 If GetLastError() = ERROR_ALREADY_EXISTS Then
   MsgBox "Already running", vbOKOnly, App.Title
   App.End
 Else 'run the application
   MsgBox "OK to run"
 End If
End Sub

Run the project, and target the remote device. Note that a message box appears that indicates that the application can be run.
While the application is still running, start it a second time from the device. By default, it exists in the "My Handheld Device" root.
Note that the application determines that an instance is already being run.