I need a Textbox with Valdiation or Preview before the Text Property is changed.

[postrondev]

I have a secure IOT application that requires to check any
input before the input is accepted.

Pure C# is required. No MVVM, React or any other "Feature"

I have studied the code and i do not understand why with 11.0
i cannot longer use a hidden textbox that i have called to
let the operations Paste/Keydown excecute and validate the
"Shadow" Text in my original Textbox.

OnKeyDown checks now for a Presenter that is new in 11.x.
For me it does not makes any sense. I guess you have spent a
lot of time for that. Why?

Would you accept an implementation of that functionality from me.

For now i am using reflection and copy/paste to implement this.