WPF Bind and populate a combobox

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WPF

combobox

Binding

I'm new to C# and WPF and my question may be too easy to some of you:
My prog crates a class member and sets its parameters reading any local xml. One of the parameters is an Int parameter. I want a combobox to handle this parameter but to show a string. My approach is to create a dictionary witch populates the combo and bind its selected value from the class member:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
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.Xml;
using System.Xml.Linq;

namespace TempProject
{
    class Dictionaries
    {
        public static Dictionary<int, string> GetChoise()
        {
            Dictionary<int, string> MyDict = new Dictionary<int, string>();
            MyDict.Add(1, "choise 1");
            MyDict.Add(2, "choise 2");
            MyDict.Add(3, "choise 3");
            return MyDict;
        }
    }

    public class MyModel : INotifyPropertyChanged
    {
        private int m_choise;

        public event PropertyChangedEventHandler PropertyChanged;
        private void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        public int Choise
        {
            get { return m_choise; }
            set
            {
                if (value < 1 || value > 3) { throw new OverflowException(); }
                m_choise = value; OnPropertyChanged("Choise");
            }
        }
    }

    public partial class MainWindow : Window
    {
        MyModel Model1 = new MyModel();
        public MainWindow()
        {
            this.InitializeComponent();
            DataContext = Model1;
        }

        private void CmdOpenXML(object sender, System.Windows.RoutedEventArgs e)
        {
            Microsoft.Win32.OpenFileDialog dlg = new Microsoft.Win32.OpenFileDialog();
            dlg.InitialDirectory = @"C:\";
            dlg.DefaultExt = ".xml";
            dlg.Filter = "XML|*.xml";
            Nullable<bool> result = dlg.ShowDialog();
            if (result == true)
            {
                XDocument xd = XDocument.Load(dlg.FileName);
                var query = from d in xd.Root.Descendants("PROJECT")
                            select d;
                foreach (var q in query)
                { Model1.Choise = Int32.Parse(q.Element("choise").Value); }
            }
        }
    }
}

and the XAML:

<Window x:Class="TempProject.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:TempProject"
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <ObjectDataProvider x:Key="MyDict"
                            ObjectType="{x:Type local:Dictionaries}"
                            MethodName="GetChoise"/>
    </Window.Resources>
    <StackPanel >
            <Menu>
                <MenuItem Header="File">
                    <MenuItem Header="Open" Click="CmdOpenXML" />
                </MenuItem>
            </Menu>
            <TextBox Text="{Binding Choise}" />
            <ComboBox ItemsSource="{Binding Source={StaticResource MyDict}}" 
                      SelectedValuePath="Key" 
                      DisplayMemberPath="Value" 
                      SelectedItem="{Binding Path=Choise,Mode=TwoWay}"/>
    </StackPanel>
</Window>

But the combo does not work correctly.
Can you tell me what am I doing wrong? Is my approach correct in general?
Can you suggest me some tutorials on the subject?
Thank you