DispatcherObject is the base class for most WPF objects that have thread affinity (e.g., UIElement, DependencyObject, Visual).

It ensures that these objects can only be accessed on the thread that created them, usually the UI thread.

Example: If you try to update a TextBox.Text from a background thread, you’ll get an InvalidOperationException — because TextBox inherits from DispatcherObject.

Dispatcher (property) → gives access to the Dispatcher associated with the object.

CheckAccess() → tells if the calling thread is the correct one.

VerifyAccess() → throws if the calling thread is not the correct one.

the role of DispatcherObject is to:

Provide thread affinity enforcement.

Provide a gateway to the Dispatcher so you can marshal calls safely onto the UI thread.

The Dispatcher is the engine that powers WPF’s single-threaded UI model.
It acts like a message pump / queue processor for the UI thread.

Association with a Thread

Each UI thread in WPF has exactly one Dispatcher.

The Application.Run() method starts the Dispatcher.Run() loop, which begins processing work items.

Message Queue

Internally, the Dispatcher maintains a priority-based queue of operations (DispatcherOperation).

Items can be enqueued using:

BeginInvoke() → async, returns immediately.

Invoke() → sync, blocks until completion

Priorities

Work is scheduled with DispatcherPriority values (e.g., Background, Normal, Render, Send).
The Dispatcher ensures higher-priority work runs earlier.
For example:

Input events → high priority.

Rendering → also high priority.

Background tasks (like data binding updates) → lower priority.

Integration with Windows Message Loop

Under the hood:

WPF’s Dispatcher.Run() hooks into the Win32 message pump.

When the OS sends messages (keyboard, mouse, paint), they are processed first.

After that, the Dispatcher checks its managed queue and executes enqueued delegates in order of priority.

Thread Safety & Marshaling

If a background thread needs to update UI:

Application.Current.Dispatcher.Invoke(() => myTextBox.Text = “Hello”);

This posts the delegate into the Dispatcher queue.

The Dispatcher eventually executes it on the UI thread.