WPF

private ShowUser showuser;
private void InvalidateSampleData(object state, EventArgs e)
{
    showuser = new ShowUser();
    Users = showuser.GetUser();
}

public class ShowUser : INotifyPropertyChanged
{
    public ObservableCollection<User> GetUser()
    {
        ObservableCollection<User> users = new ObservableCollection<User>();

        SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings[
            "dLondre.Properties.Settings.CSLONDRE"].ConnectionString);

        string str = "";
        str += "SELECT userid,firstname + ' ' + lastname as name FROM [user] ";

        SqlCommand com = con.CreateCommand();
        com.CommandText = str;

        try
        {
            con.Open();
            SqlDataReader sdr = com.ExecuteReader();
            while (sdr.Read())
            {
                users.Add(new User { UserID = (string)sdr["userid"], FirstName = (string)sdr["name"] });
            }

            com.Dispose();
            con.Close();
            con.Dispose();
        }
        catch (Exception e)
        {
            Console.WriteLine(e);
        }

        return users;
    }

    #region Methods
    public event PropertyChangedEventHandler PropertyChanged;
    protected void OnPropertyChanged(string name)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(name));
        }
    }
    #endregion
}

private ObservableCollection<User> _users;
public ObservableCollection<User> Users
{
    get { return _users; }
    set
    {
        if (value != _users)
            _users = value;
        OnPropertyChanged("Users");
    }
}

User _user;
public User SelectedUserID
{
    get { return _user; }
    set
    {
        _user = value;
        OnPropertyChanged("SelectedUserID");
        //MessageBox.Show("Do your Task with " + value.UserID);
    }
}

private void LoadDataVoidOnPageWichContainsYourComboBoxItemSource()
{
    ComboUserData.CollectionChanged += ComboUserData_CollectionChanged;
}

void ComboUserData_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
{
    OnPropertyChanged("ComboUserData");
}

<Hyperlink NavigateUri="{Binding Caption}"
           Foreground="#0C2DAA"
           Style="{StaticResource linkStyle}"
           CommandParameter="{Binding}"
           Command="{Binding Path=DataContext.SelectedNodeCommand,
                    RelativeSource={RelativeSource FindAncestor,
                    AncestorType={ x:Type views:JobListView}}}">

    <InlineUIContainer>
        <TextBlock Text="{Binding Caption}" />
    </InlineUIContainer>

</Hyperlink

<HierarchicalDataTemplate DataType="{x:Type models:JobSummaryModel}"
                            ItemsSource="{Binding Path=Nodes}">
    <Grid Margin="2">

        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="Auto"/>
            <ColumnDefinition Width="Auto"/>
        </Grid.ColumnDefinitions>

        <Image Source="/FMG.UI.WPF.Shared;component/Media/Images/job_72.png"
                Grid.Column="0"
				Height="16"
				Width="16"
                Margin="0,0,3,0"/>

        <TextBlock Grid.Column="1">
            <Hyperlink NavigateUri="{Binding Caption}"
                        Foreground="#0C2DAA"
                        Style="{StaticResource linkStyle}"
                        CommandParameter="{Binding}"
                        Command="{Binding Path=DataContext.SelectedNodeCommand,
                                RelativeSource={RelativeSource FindAncestor, 
                                AncestorType={ x:Type views:JobListView}}}">

                <InlineUIContainer>
                    <TextBlock Text="{Binding Caption}" 
                                FontSize="12"/>
                </InlineUIContainer>

            </Hyperlink>
        </TextBlock>
    </Grid>
</HierarchicalDataTemplate>