Question

What’s the first line of the following code called?

[DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
public virtual IController Controller
{
    get { return controller; }
    set { controller = value; }
}

Answer 1

It’s called an attribute. Attributes are used to describe properties, methods, etc. They serve to provide metadata, among other things.

In this case, the DesignerSerializationVisibility.Hidden attribute means that the Controller property isn’t visible to the design-time serializer.