Passing data between WinForms forms [duplicate]

Answer 1

I just changed it to this:
add.cs:

 public string optionType { get; set; }
 public string optionName { get; set; }
 public string optionURL { get; set; }
 public string optionInterval { get; set; }
 public int yCoord { get; set; }

Answer 2

If you need to know about the changed value before closing the child form, a custom event will let you inform the parent form elegantly.

Here's a great tutorial on delegates and events in C#

http://www.akadia.com/services/dotnet_delegates_and_events.html

Once the child form is instantiated, the parent form would register to receive one or more custom events (as needed) from the child.

Another methodology is to pass a reference to the parent form into the child form so that the child can invoke a function or property of the parent to inform about the change. However, that approach creates a tight coupling between the two forms and is discouraged.