Best practice when you need two user controls (winforms) to communicate

Question

Extended problem

I would like to add a new problem in addition to the original problem specified below. One of the user controls in the application cont

Answer 1

1. Expose the data it as a property.
2. Create a property on the other user control that the parent form will populate with the reference to the control with the data.

Pseudo code:

public UserControlA uca { get; set; }
...

var items = uca.Items;