WPF

if (true)
{
   ChildForm frm = new ChildForm();
   frm.ShowDialog(this); // Modal accsess
   MessageBox.Show(frm.StringToGet();
}
// MessageBox.Show(frm.StringToGet(); // This is outside scope of frm. Here form no longer exsist

public static class staticClass
{
   static staticClass() // static class constructior
   {
      SomeText = "Intalized in constructior";
   }
   static ~staticClass(){} // destructor of static class

   public static String SomeText;
}

// parentForm
if (true)
{
   MessageBox.Show(staticClass.SomeText); // returns Intalized in constructior
   ChildForm.ShowDialog(); 
   MessageBox.Show(staticClass.SomeText); // returns other string that was changed in child form
}

class LanguageItem
    {
        public int ID { get; set; }
        public string Word { get; set; }
    }

ObservableCollection<LanguageItem> words = new ObservableCollection<LanguageItem>();
       public ObservableCollection<LanguageItem> Words
       {
           get
           {
               return words;
           }
           set
           {
               if (words != value)
               {
                   words = value;
                   NotifyPropertyChanged("Words");
               }
           }
       }

<Label Content="{Binding Path=Words[0].Word}"/>
<Label Content="{Binding Path=Words[1].Word}" Grid.Column="1"/>

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.ComponentModel;
using System.IO;

namespace SwitchLanguage
{
    public partial class MainWindow : Window, INotifyPropertyChanged
    {
        string folderPath = @"C:\Users\SwitchLanguage\";
        ObservableCollection<LanguageItem> words;
        public event PropertyChangedEventHandler PropertyChanged;

        public MainWindow()
        {
            InitializeComponent();

            // Must instance event or else PropertyChanged is ALWAYS null
            PropertyChanged += new PropertyChangedEventHandler(MainWindow_PropertyChanged);
        }


        private void btnUK_Click(object sender, RoutedEventArgs e)
        {
            ReadFile("UK.txt");
        }

        private void btnUS_Click(object sender, RoutedEventArgs e)
        {
            ReadFile("US.txt");
        }



        private void ReadFile(string file)
        {
            if (!File.Exists(folderPath + file))
            {
                throw new FileNotFoundException("Language file doesn't exist");
            }

            StreamReader sr = new StreamReader(folderPath + file);
            ObservableCollection<LanguageItem> words = new ObservableCollection<LanguageItem>();

            while (!sr.EndOfStream)
            {
                string[] parts = sr.ReadLine().Split('=');

                LanguageItem languageItem = new LanguageItem();
                languageItem.ID = int.Parse(parts[0]);
                languageItem.Word = parts[1];
                words.Add(languageItem);
            }

            Words = words;

            sr.Close();
        }

        public ObservableCollection<LanguageItem> Words
        {
            get { return words; }
            set
            {
                if (words != value)
                {
                    words = value;
                    PropertyChanged(this, new PropertyChangedEventArgs("Words"));
                }
            }
        }

        void MainWindow_PropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            Console.WriteLine("");
        }
    }

    public class LanguageItem
    {
        public int ID { get; set; }
        public string Word { get; set; }
    }
}

<Window x:Class="SwitchLanguage.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <Label Name="lblWord" Content="{Binding Path=Words[0].Word}" Margin="50,-100,0,0" Width="200" Height="30"></Label>
        <Button Width="100" Height="40" Click="btnUK_Click" Content="UK" Margin="-100,0,0,0"></Button>
        <Button Width="100" Height="40" Click="btnUS_Click" Content="US" Margin="100,0,0,0"></Button>
    </Grid>
</Window>

DataContext = this;

Pete O'Hanlon wrote:

We use a custom localisable MarkupExtension to handle this