Custom code in designer.vb file goes away when making edits in design mode

I have a form named "form1" in vb.net. This form has many controls. I opened the form1.designer.vb file and put in an if else expression such as:

If getLanguage() = "en" then label1.text = "Good Morning" Else label1.Text = "Bonjour"

This works perfectly fine in runtime.

If I open the Form1.vb [Design] page in design, and make any changes, the code above disappears.

Is there a way I can keep any code I put in the designer page? I don't want to put them in the load event in the form1.vb file.

Solution

Locate this code :

    Public Sub New()
        Me.InitializeComponent()
    End Sub

Then add a line :

    Public Sub New()
        Me.InitializeComponent()
        Me.MakeComponentsChanges()
    End Sub

Then create the method in form1.vb or another Partial Class copy of your creation :

    Private Sub MakeComponentsChanges()
        If getLanguage() = "en" then
            label1.text = "Good Morning"
        Else
            label1.Text = "Bonjour"
        End If
    End Sub

Don't touch the form1.designer.vb (.cs)

And as stated in other answers, better use .Localizable Property in the IDE and change it from False to True. Then you'll gain access to several default languages. You don't have to bother writing code.

Select ONE language to start with : English for example.
Then edit each one of your controls Text : write "Hello" in a button, "Good Morning" in a Label, "Because I'm Happy" in a MenuItem etc.
Then change the language again, select French.
Then edit again each control and write "Bonjour", "Je vous souhaite un bon matin", "Parceque je suis de bonne humeur".... YES you've lost the previous text but have faith !
Compile your project without launching it, and you'll see the IDE has created two new files : Form1.en.resx and Form1.fr.resx (or so) along with Form1.vb and Form1.Designer.vb. Don't edit them !

If you open the en.resx or fr.resx, you'll see that the edits you've made are in there. Those files are used to store inbuilt Lang-related ressources for your form. That's flatly called Globalization.

Then locate again the constructor of your Form.

    Public Sub New()
        Me.InitializeComponent()
        'Me.MakeComponentsChanges()
        ' Now you know about some Globalization, 
        ' you may get rid of that Method.

        ' Add two variables :
        Dim OriginalCulture As CultureInfo
        Dim CurrentOSCulture As CultureInfo

        ' Initialize them
        OriginalCulture = Thread.CurrentThread.CurrentCulture
        CurrentOSCulture = CultureInfo.CurrentCulture

        ' Do this test :
        Try
            Thread.CurrentThread.CurrentCulture = CurrentOSCulture ' may fail
            Thread.CurrentThread.CurrentUICulture = CurrentOSCulture ' may fail
            ' Attempt to match the current Thread culture to the Operating System one.
        Catch CurrentException As Exception
            Thread.CurrentThread.CurrentCulture = OriginalCulture
            Thread.CurrentThread.CurrentUICulture = OriginalCulture
            ' If it fails, revert back to default as defined in your IDE
        End Try
    End Sub

Don't forget to add on top of your Class declaration those two namespaces :

Imports System.Globalization
Imports System.Threading

And voilà ! I know I said you don't have to bother writing code, but the bits above in the constructor are enough to handle the selection of a language. Plus besoin de taper du code superflu après ça.