В файле App.xaml:

<Application x:Class="MyTBot_FW.App"

xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

xmlns:local="clr-namespace:MyTBot_FW"

StartupUri="View/MainView.xaml">

<Application.Resources>

</Application.Resources>

</Application>

Или в App.xaml.cs

public partial class App : Application

{

protected override void OnStartup(StartupEventArgs e)

{

base.OnStartup(e);

View.MainWindow mv = new View.MainWindow();

mv.Show();

}

}