In WPF (Windows Presentation Foundation), the framework is organized into a small set of core assemblies that provide UI, graphics, layout, media, and integration features.

✅ Core WPF Assemblies

1️⃣ PresentationFramework.dll

📌 Purpose:
This is the main WPF assembly used by most applications.

Contains:

• Application & Window classes

• Controls (Button, TextBox, Label, DataGrid, etc.)

• Data Binding

• Styles, Templates, Resources

• Navigation (Page, Frame)

👉 Without this, you can’t build a typical WPF UI.

2️⃣ PresentationCore.dll

📌 Purpose:
Provides the low-level rendering and media services.

Contains:

• Visual & UIElement base classes

• Graphics rendering

• Animation support

• 2D/3D graphics

• Imaging (BitmapImage, DrawingImage)

👉 Acts as a bridge between WPF UI and DirectX.

3️⃣ WindowsBase.dll

📌 Purpose:
Provides base types and infrastructure for WPF.

Contains:

• DependencyObject

• DependencyProperty

• Dispatcher

• RoutedEvent

• Threading & timing services

👉 This assembly is shared with other .NET technologies too.

4️⃣ System.Xaml.dll

📌 Purpose:
Handles XAML parsing and processing.

Contains:

• XAML reader & writer

• Markup extensions

• XAML serialization

👉 Converts XAML into runtime objects.

🧩 Supporting / Optional Assemblies

📌 Interview-Friendly One-Line Answer

Core WPF assemblies are:
PresentationFramework.dll, PresentationCore.dll, WindowsBase.dll, and System.Xaml.dll