Changing content dynamically in wpf window

You can put the content of the window into a UserControl. Your window then only has a content-control and a button to change the content. On a click on the button you can reassign the content-property of the content-control.

I've made a small example for this.

The XAML-Code for your MainWindow can look like this:

<Window x:Class="WpfApplication3.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>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        <Button Content="Switch" Click="ButtonClick"/>
        <ContentControl x:Name="contentControl" Grid.Row="1"/>
    </Grid>
</Window>

I've added two UserControls to the solution. The CodeBehind for the MainWindow looks like:

    public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        this.contentControl.Content = new UserControl1();
    }

    private void ButtonClick(object sender, RoutedEventArgs e)
    {
        this.contentControl.Content = new UserControl2();
    }
}

Update I've created a small usercontrol called MyUserControl. The xaml-markup looks like

<UserControl x:Class="WpfApplication.MyUserControl"
             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" 
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300">
    <StackPanel Orientation="Vertical">
        <Label Content="This is a label on my UserControl"/>
        <StackPanel Orientation="Horizontal" HorizontalAlignment="Left">
            <Button Content="Testbutton 1" Margin="5"/>
            <Button Content="Testbutton 2" Margin="5"/>
        </StackPanel>
        <CheckBox Content="Check Me"/>
    </StackPanel>
</UserControl>

In the button-click-event above you can assign a new instance of this usercontrol to the content-control. This you can do by:

this.contentControl.Content = new MyUserControl();