add code

ISwitchable.cs

@@ -0,0 +1,13 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace PageSwitcher
+{
+    interface ISwitchable
+    {
+        void UtilizeState(object state);
+    }
+}

MainWindow.xaml.cs

@@ -23,6 +23,27 @@ namespace PageSwitcher
         public MainWindow()
         {
             InitializeComponent();
+            Switcher.pageSwitcher = this;
+            Switcher.Switch(new UserControl1());
+        }
+
+        public void Navigate(UserControl nextPage)
+        {
+            this.Content = nextPage;
+        }
+
+        public void Navigate(UserControl nextPage, object state)
+        {
+            this.Content = nextPage;
+            ISwitchable s = nextPage as ISwitchable;
+            
+            if (s != null)
+            {
+                s.UtilizeState(state);
+            } else
+            {
+                throw new ArgumentException("NextPage is not ISwichable! " + nextPage.Name.ToString());
+            }
         }
     }
 }

PageSwitcher.csproj

@@ -55,6 +55,13 @@
       <Generator>MSBuild:Compile</Generator>
       <SubType>Designer</SubType>
     </ApplicationDefinition>
+    <Compile Include="Switcher.cs" />
+    <Compile Include="UserControl1.xaml.cs">
+      <DependentUpon>UserControl1.xaml</DependentUpon>
+    </Compile>
+    <Compile Include="UserControl2.xaml.cs">
+      <DependentUpon>UserControl2.xaml</DependentUpon>
+    </Compile>
     <Page Include="MainWindow.xaml">
       <Generator>MSBuild:Compile</Generator>
       <SubType>Designer</SubType>
@@ -63,10 +70,19 @@
       <DependentUpon>App.xaml</DependentUpon>
       <SubType>Code</SubType>
     </Compile>
+    <Compile Include="ISwitchable.cs" />
     <Compile Include="MainWindow.xaml.cs">
       <DependentUpon>MainWindow.xaml</DependentUpon>
       <SubType>Code</SubType>
     </Compile>
+    <Page Include="UserControl1.xaml">
+      <SubType>Designer</SubType>
+      <Generator>MSBuild:Compile</Generator>
+    </Page>
+    <Page Include="UserControl2.xaml">
+      <SubType>Designer</SubType>
+      <Generator>MSBuild:Compile</Generator>
+    </Page>
   </ItemGroup>
   <ItemGroup>
     <Compile Include="Properties\AssemblyInfo.cs">

Switcher.cs

@@ -0,0 +1,23 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.Windows.Controls;
+
+namespace PageSwitcher
+{
+    public static class Switcher
+    {
+        public static MainWindow pageSwitcher;
+        public static void Switch(UserControl newPage)
+        {
+            pageSwitcher.Navigate(newPage);
+        }
+
+        public static void Switch(UserControl newPage, object state)
+        {
+            pageSwitcher.Navigate(newPage, state);
+        }
+    }
+}

UserControl1.xaml

@@ -0,0 +1,13 @@
+<UserControl x:Class="PageSwitcher.UserControl1"
+             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:PageSwitcher"
+             mc:Ignorable="d" 
+             d:DesignHeight="300" d:DesignWidth="300">
+    <Grid>
+        <Button x:Name="button1" Content="Button" Margin="108,137,117,143" Click="button1_Click"/>
+
+    </Grid>
+</UserControl>

UserControl1.xaml.cs

@@ -0,0 +1,33 @@
+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 PageSwitcher
+{
+    /// <summary>
+    /// Interaction logic for UserControl1.xaml
+    /// </summary>
+    public partial class UserControl1 : UserControl
+    {
+        public UserControl1()
+        {
+            InitializeComponent();
+        }
+
+        private void button1_Click(object sender, RoutedEventArgs e)
+        {
+            Switcher.Switch(new UserControl2());
+        }
+    }
+}

UserControl2.xaml

@@ -0,0 +1,14 @@
+<UserControl x:Class="PageSwitcher.UserControl2"
+             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:PageSwitcher"
+             mc:Ignorable="d" 
+             d:DesignHeight="300" d:DesignWidth="300">
+    <Grid>
+        <Button x:Name="button" Content="Button" Margin="113,138,112,142" Click="button_Click"/>
+        <Label x:Name="label" Content="c2" HorizontalAlignment="Left" Margin="113,107,0,0" VerticalAlignment="Top"/>
+
+    </Grid>
+</UserControl>

UserControl2.xaml.cs

@@ -0,0 +1,33 @@
+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 PageSwitcher
+{
+    /// <summary>
+    /// Interaction logic for UserControl2.xaml
+    /// </summary>
+    public partial class UserControl2 : UserControl
+    {
+        public UserControl2()
+        {
+            InitializeComponent();
+        }
+
+        private void button_Click(object sender, RoutedEventArgs e)
+        {
+            Switcher.Switch(new UserControl1());
+        }
+    }
+}