VB.NET: Run a method only once in the Application's life time.

Question

I'm making a Library type app which needs to scan the whole computer when it is run for the first time. Not again ever. How can I accomplish it?

I'll be using SQL database to store data. So, I can easily make a table there and store a flag and check it on first run, but is there any other way? Any native support for this in VB.NET?

Answer 1

EDIT: If you're looking for a way to determine, using some native feature of VB.NET, whether a method has ever been run before (as in, last year), I think you're out of luck. That said, a quick-and-dirty approach might be to define a method to query the database for the flag you've referred to and store the result of that method in a static flag.

Public Sub MethodToRunOnlyOnce()
    ' this flag will maintain its value between method calls '
    ' in the same session '
    Static methodAlreadyRun As Boolean = MethodHasBeenRun()

    If methodAlreadyRun Then
        Exit Sub
    End If

    Try
        ' ... code ... '
    Finally
        MethodToSetDatabaseFlag()
        methodAlreadyRun = True
    End Try
End Sub

Private Sub MethodToSetDatabaseFlag()
    ' code here to set Db flag '
End Sub

Private Function MethodHasBeenRun() As Boolean
    ' code here to check Db flag '
End Function

Answer 2

Using your SQL database seems like a viable solution. You can also write a flag to a settings file on the file system if you don't want to use a table to hold it. This is a pretty good site with some examples on how to write to a file.

http://www.freevbcode.com/ShowCode.asp?ID=4492

Answer 3

You could always store this flag in an xml file or in the registry so it's on the PC. If you store it in a database and there are multiple copies of this program running on different PCs, you would have to identify them in the DB somehow, whereas if you keep track of it locally you don't need to worry about it.

Answer 4

Use either

Deployment.Application.ApplicationDeployment.CurrentDeployment.IsFirstRun

or

My.Application.Deployment.IsFirstRun

Edit:

Check this article for additional info.

Answer 5

I found the best way to be to use appsettings..