How to change app language at runtime

This guide will walk you through the necessary steps for changing app language at runtime.

[!TIP] The complete source code that goes along with this guide is available in the unoplatform/Uno.Samples GitHub repository - RuntimeCultureSwitching sample

Prerequisites

Make sure to setup your environment first by following our instructions.

Steps to change application language at runtime

[!NOTE] This guide is an extension of "How to use localization", and will build on top the sample from that guide. Make sure you have completed the previous guide or downloaded the full localization sample, before continuing.

1. Add two new pages to the Localization.Shared project by: Right-click on Localization.Shared > Add > New Item ... > Visual C# > XAML > Blank Page And, name them Page1 and LanguageSettings

2. Add some content to the two new pages:

   • Page1.xaml:

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     <Page x:Class="UnoLocalization.Page1"
           xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
           xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
           xmlns:toolkit="using:Uno.UI.Toolkit">
     
         <StackPanel toolkit:VisibleBoundsPadding.PaddingMask="Top">
             <TextBlock x:Uid="Page1_Title" Text="Page one" FontSize="30" />
     
             <Button x:Uid="Page1_GoBack" Content="Go back" Click="GoBack" />
         </StackPanel>
     </Page>
     

   • Page1.xaml.cs:

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     private void GoBack(object sender, RoutedEventArgs e) => Frame.GoBack();
     

   • LanguageSettings.xaml:

     xmlCopy

     <Page x:Class="UnoLocalization.LanguageSettings"
           xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
           xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
           xmlns:toolkit="using:Uno.UI.Toolkit">
     
         <StackPanel toolkit:VisibleBoundsPadding.PaddingMask="Top">
             <TextBlock x:Uid="LanguageSettings_Title" Text="Language Settings" FontSize="30" />
     
             <Button Content="English" Click="SetAppLanguage" Tag="en" />
             <Button Content="Français" Click="SetAppLanguage" Tag="fr" />
     
             <Button x:Uid="LanguageSettings_GoBack"
                     Content="Go back"
                     Click="GoBack"
                     Margin="0,12,0,0"/>
         </StackPanel>
     </Page>
     

   • LanguageSettings.xaml.cs:

     csharpCopy

     private void SetAppLanguage(object sender, RoutedEventArgs e)
     {
         if ((sender as Button)?.Tag is string tag)
         {
             // Change the app language
             Windows.Globalization.ApplicationLanguages.PrimaryLanguageOverride = tag;
     
             // Clear the back-navigation stack, and send the user to MainPage
             // This is done because any loaded pages (MainPage(in back-stack) and LanguageSettings (current active page))
             // will stay in the previous language until reloaded.
             Frame.BackStack.Clear();
             Frame.Navigate(typeof(MainPage));
         }
     }
     
     private void GoBack(object sender, RoutedEventArgs e) => Frame.GoBack();
     

3. Add two new buttons to MainPage for navigation:

   • MainPage.xaml:

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     <StackPanel toolkit:VisibleBoundsPadding.PaddingMask="Top">
         <TextBlock x:Uid="MainPage_IntroText" Text="Hello, world!" Margin="20" FontSize="30" />
         <TextBlock x:Name="CodeBehindText" Text="This text will be replaced" />
     
         <Button x:Uid="MainPage_GotoNextPage" Content="Next Page" Click="GotoNextPage" />
         <Button x:Uid="MainPage_GotoLanguageSettings" Content="Language Settings" Click="GotoLanguageSettings" />
     </StackPanel>
     

   • MainPage.xaml.cs:

     csharpCopy

     private void GotoNextPage(object sender, RoutedEventArgs e) => Frame.Navigate(typeof(Page1));
     private void GotoLanguageSettings(object sender, RoutedEventArgs e) => Frame.Navigate(typeof(LanguageSettings));
     

4. Add a new folder fr under the Strings folder by: Right-click on String > Add > New Folder

5. Add a new resource file Resources.resw under the fr folder by: Right-click on fr > Add > New Item ... > Visual C# > Xaml > Resources File

6. Add the localization strings for the new elements: Open both Strings\en\Resources.resw and Strings\fr\Resources.resw, and add these:

   Name	Value in en\Resources.resw	Value in fr\Resources.resw
   MainPage_GotoNextPage.Content	Next Page	Page suivante
   MainPage_GotoLanguageSettings.Content	Language Settings	Paramètres de langue
   Page1_Title.Text	Page in english	Page en français
   Page1_GoBack.Content	Go back	Retourner
   LanguageSettings_Title.Text	Language Settings	Paramètres de langue
   LanguageSettings_GoBack.Content	Go back	Retourner

Get the complete code

See the completed sample on GitHub: RuntimeCultureSwitching

Additional Resources

• Globalization and localization

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