SampleWPF

Construct.xaml.cs

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;

namespace Demo
{
    /// <summary>
    /// Interaction logic for Construct.xaml
    /// </summary>
    public partial class Construct : Page
    {
        public string[] Characters = new string[3] { "aang.jpg", "katara.jpg", "toph.jpg" };
        public Random R = new Random();
        public int c = 0;
        public Construct()
        {
            InitializeComponent();
        }

        private void Character_Checked(object sender, RoutedEventArgs e)
        {
            // which button was clicked?
            var button = sender as RadioButton;
            

            //what to do with selection?
            switch (button.Content.ToString())
            {
                case "Aang":
                    c = 0;
                    break;

                case "Katara":
                    c = 1;
                    break;

                case "Toph":
                    c = 2;
                    break;
            }
        }

        private void btnLoad_Click(object sender, RoutedEventArgs e)
        {
            recChar.Fill = new ImageBrush
            {
                ImageSource = new BitmapImage(new Uri(@"pack://application:,,,/Demo;component/img/" + Characters[c], UriKind.Absolute))
            };
        }

        private void btnRand_Click(object sender, RoutedEventArgs e)
        {
            c = R.Next(0, Characters.Length);
            recChar.Fill = new ImageBrush
            {
                ImageSource = new BitmapImage(new Uri(@"pack://application:,,,/Demo;component/img/" + Characters[c], UriKind.Absolute))
            };

        }
    }
}

MainWindow.xaml

<Window x:Class="Demo.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:Demo"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid Background="DarkSeaGreen">
        <Frame x:Name="Navigation" NavigationUIVisibility="Hidden" />
    </Grid>
</Window>

MainWindow.xaml.cs

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;

namespace Demo
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            Navigation.Navigate(new Welcome());
        }
    }
}

Welcome.xaml

<Page x:Class="Demo.Welcome"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
      xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
      xmlns:local="clr-namespace:Demo"
      mc:Ignorable="d" 
      d:DesignHeight="450" d:DesignWidth="800"
      Title="Welcome">

    <Grid>
        <TextBlock HorizontalAlignment="Left" Margin="85,128,0,0" TextWrapping="Wrap" Text="Character Chooser" VerticalAlignment="Top" Height="118" Width="610" FontSize="72" Foreground="White"/>
        <Button x:Name="btnStart" Content="Start" HorizontalAlignment="Left" Margin="333,272,0,0" VerticalAlignment="Top" Width="99" Background="{x:Null}" Foreground="White" FontSize="22" Height="37" Click="btnStart_Click" BorderBrush="{x:Null}"/>
        <Button x:Name="btnQuit" Content="Quit" HorizontalAlignment="Left" Margin="333,325,0,0" VerticalAlignment="Top" Width="99" BorderBrush="{x:Null}" Foreground="White" Background="{x:Null}" FontSize="22" Click="btnQuit_Click"/>

    </Grid>
</Page>

Welcome.xaml.cs

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;

namespace Demo
{
    /// <summary>
    /// Interaction logic for Welcome.xaml
    /// </summary>
    public partial class Welcome : Page
    {
        public Welcome()
        {
            InitializeComponent();
        }

        private void btnStart_Click(object sender, RoutedEventArgs e)
        {
            NavigationService.Navigate(new Uri("Construct.xaml", UriKind.Relative));
        }

        private void btnQuit_Click(object sender, RoutedEventArgs e)
        {
            Environment.Exit(0);
        }
    }
}