Keep settings in sync between forms application and windows service (or any n-tier, really)

Question

I have a Windows Service that performs a number of periodic activities, and I want to change the settings of this service from a Windows Forms app. I\'m not sure, though, ab

Answer 1

I kinda use your number 2.

But I'm only working in .NET 2 with my application, but it should still apply.

I have a settings class that I use across my 2 programs. Inside this settings class I setup a FileSystemWatcher object that looks at the Settings file.

If the settings file is updated by the other application, my current gets an event trigger to indicate that the settings need to reload.

You can also apply the same principle in your settings screen so that if the (service) other application updates anything during the settings edit, that is reflected in your screen.

I use the AppData (my company/application name directory) to store the file.

The other thing to bear in mind, is that there can be locking on the file while it is being written so you can either use a temp name save, delete old, rename temp method or put some protective locking on the file when reading after the filewatcher event fires that changes have been made.

I use this approach in my FileSystemWatcher before proceeding

IPSDependency.FileSystem.WaitForLockOnFile(Me.mFilePath)

the code for that is like this. (upon reading this now, there may be a better method my using some sleep in here to reduce CPU thrashing)

Public Shared Function IsLockAvailable(ByVal filename As String, ByVal fnfIsOK As Boolean) As Boolean
    Dim fi As FileInfo
    fi = New FileInfo(filename)
    Return IsLockAvailable(New FileInfo(filename), fnfIsOK)
End Function

Public Shared Function IsLockAvailable(ByVal theFile As FileInfo, ByVal fnfIsOK As Boolean) As Boolean
    Dim fs As FileStream
    Try
        If theFile.Exists Then
            fs = New FileStream(theFile.FullName, FileMode.Open, FileAccess.ReadWrite, FileShare.None)
            fs.Close()
            Return True
        Else
            Return fnfIsOK
        End If
    Catch ex As IOException
        'we just let the exception go, because we are only testing the file rather than trying to use it.
        Return False
    End Try
End Function

Public Shared Sub WaitForLockOnFile(ByVal theFilename As String)
    WaitForLockOnFile(New FileInfo(theFilename))
End Sub

Public Shared Sub WaitForLockOnFile(ByVal theFile As FileInfo)
    Dim lockAvailable As Boolean
    If theFile.Exists Then
        While Not lockAvailable
            lockAvailable = IsLockAvailable(theFile, False)
        End While
    End If
End Sub