Toggle two views (Windows) in MVVM WPF
/// <summary>
    ///   Application_Startup
    /// </summary>
    /// <param name = "sender"></param>
    /// <param name = "e"></param>
    private void Application_Startup(object sender, StartupEventArgs e)
    {
        log.Debug("Application_Startup  " + Utility.FUNCTION_ENTERED_LOG);
        try
        {

                if (e.Args.Length == 0)
                {
                    AboutDialog.SpashScreen(Utility.TOOL_NAME,
                                            Utility.TOOL_VERSION);
                    MainView mainForm = new MainView();
                    mainForm.ShowDialog();
                }
                else
                {
                    string key = null;
                    foreach (string arg in e.Args)
                    {
                        if (arg.StartsWith("-"))
                        {
                            //this is a key
                            key = arg;
                            if (key.Equals("-config"))
                            {
                                CommandLineArgs.Add(key, "config");
                                break;
                            }
                            if (key.Equals("-start"))
                            {
                                CommandLineArgs.Add(key, "start");
                            }
                        }
                        else
                        {
                            //should be a value
                            if (key == null)
                            {
                                throw new Exception(
                                    "The command line arguments are malformed.");
                            }
                            CommandLineArgs.Add(key, arg);
                            key = null;
                        }
                    }
                    string config = string.Empty;
                    foreach (object k in App.CommandLineArgs.Keys)
                    {
                        config += CommandLineArgs[k].ToString();
                    }

                    switch (config)
                    {
                        case "config":
                            AboutDialog.SpashScreen(
                                Utility.TOOL_NAME,
                                Utility.TOOL_VERSION);
                            MainView mainForm = new MainView();
                            mainForm.ShowDialog();
                            break;
                         case "start" :
                               ExecutionForm execuForm= new ExecutionForm();
                               execuForm.ShowDialog();
                               break;
                        default:
                            MessageBox.Show("Incorrect Parameters",
                                            Utility.TOOL_NAME);
                            Application.Current.Shutdown();
                            break;
                    }

            }
            log.Debug("Application_Startup" + Utility.FUNCTION_EXIT_LOG);
        }
        catch (Exception ex)
        {
            log.Error("Application_Startup" + ex.Message, ex);
        }
    }

<DockPanel LastChildFill="true">
    <Menu DockPanel.Dock="Top" ...>
    </Menu>
    <ContentControl Content="{Binding}" ... />
</DockPanel>

<Window.Resources>
     <DataTemplate x:Key="ConfigView" ... />
     <DataTemplate x:Key="ExecutionView" ... />
</Window.Resources>

public class ViewModel : INotifPropertyChanged
{
    private string mode;

    public string Mode
    {
         get  { return mode; }
         set  { mode = value; NotifPropertyChanged("Mode"); }
    }

    private IComamnd changeModeCommand;

    public ICommand ChangeModeCommand
    {
        get
        {
            if (changeModeCommand == null)
                 changeModeCommand
                    = new DelegateCommand(
                         OnModeChange,
                         CanModeChange);
            return changeModeCommand;
        }
    }

    //// Other properties and functions go here ...
}

<Window.InputBindings>
    <KeyBinding Command="{Binding ChangeModeCommand}"
                Key="F12" />
</Window.InputBindings>

<ContentControl Content="{Binding}">
    <ContentControl.Style>
        <Style TargetType="{x:Type ContentControl}">
            <Style.Triggers>
                <DataTrigger Binding="{Binding Mode}" Value="Config">
                    <Setter Property="ContentTemplate"
                            Value="{StaticResource ConfigView}"/>
                </DataTrigger>
                <DataTrigger Binding="{Binding Mode}" Value="Execution">
                    <Setter Property="ContentTemplate"
                            Value="{StaticResource ExecutionView}"/>
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </ContentControl.Style>
  </ContentControl>