cannot Localize .aspx containg devex controls though the pages with asp controls were localized successfully

Fortunately, ASP.NET provides a method in the Page class to override: InitializeCulture(). This method executes very early in the page lifecycle (much before any control is generated), and here we can set the UICulture and Culture of the current thread.
Since this method is in the Page class and I do not want to repeat the same code for each web page, I created a BasePage class, and all the aspx pages in my application derive from this BasePage class.

Protected Overrides Sub InitializeCulture()
        Try
            If (Not String.IsNullOrEmpty(Session("language"))) Then
                Thread.CurrentThread.CurrentCulture = New CultureInfo(Session("language").ToString)
                Thread.CurrentThread.CurrentUICulture = Thread.CurrentThread.CurrentCulture
            Else
                Thread.CurrentThread.CurrentUICulture = New CultureInfo("en-US")
                Thread.CurrentThread.CurrentCulture = New CultureInfo("en-US")
            End If
        Catch ex As Exception
        End Try
        MyBase.InitializeCulture()
    End Sub