I have a WPF .NET 4 application where I override the `OnStartup` method in order to process the file passed to my application. However, it seems that this method is not being called when the application runs. I put an exception in there and even a breakpoint and it starts up and completely ignores this.

Am I missing something?

Code for App.xml.cs:

```
/// <summary>
/// Interaction logic for App.xaml
/// </summary>
public partial class App : Application
{
    protected override void OnStartup(StartupEventArgs e)
    {
        throw new NotImplementedException();
    }
}

```

Contents of App.xaml:

```
<Application x:Class="XGN_Image_Downloader.App"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         StartupUri="MainWindow.xaml">
<Application.Resources>

</Application.Resources>
</Application>

```

**EDIT:** Found it! The x:Class attribute in App.xaml did not match the App.xaml.cs class :) That's what you get for coding while drinking wine. (Thanks to this thread: [WPF app startup problems](https://stackoverflow.com/questions/2874920/wpf-app-startup-problems))