Why is my System.Windows namespace missing RoutedEventArgs? In Visual Studio it only contains System-CodePudding

I recently downloaded Unity and Visual Studio and are attempting to integrate the NoesisGUI framework into my project. It requires the System.Windows.RoutedEventArgs class, but the only class I can see in System.Windows is Input. I've googled around and it looks like RoutedEventArgs should be in the 4.8 .net framework and I've verified my Visual Studio .net version is 4.8.3928.0.

It is worth noting that in my References section of the Solutions tab, it has a hundred different System .dll references listed (including System.Windows), but not System.Windows.RoutedEventArgs.

Here's some of the reference code, although I've removed anything that isn't important.

using System;
using System.Windows.Controls;

namespace Dummy_Project
{
    public partial class Dummy_ProjectMainView : UserControl
    {
        private void Button_Click(object sender, System.Windows.RoutedEventArgs e)
        {

        }
    }
}

I tried downloading the .net 4.8 framework and installing that, but it was still missing. I also tried unloading the project multiple times as per

...which will allow you to create a new Unity app utilising Noesis:

Designing in Visual Studio:

Seeing the results in Unity:

(images sourced from Which then needs the 'System.Windows.Automation' namespace, but I couldn't see which dll that was defined in. But that's my point.

NOW, with in relation to NoesisGUI specifically... have you noticed that the project already contains a 'proxy' for RoutedEventArgs? There's a file in "NoesisGUI/Plugins/API/Proxies" called RoutedEventArgs.cs.

Edit: I made the assumption that you had used the asset from the Unity Asset Store here: https://assetstore.unity.com/packages/tools/gui/noesisgui-2-2-9282. It seems that there might be another NoesisGUI project, and that you might have been using that one instead?