The add contextual keyword (C# Reference)

The add contextual keyword is used to define a custom event accessor that is invoked when client code subscribes to your event. If you supply a custom add accessor, you must also supply a remove accessor.

The following example shows an event that has custom add and remove accessors. For the full example, see How to implement interface events.

class Events : IDrawingObject
{
    event EventHandler PreDrawEvent;

    event EventHandler IDrawingObject.OnDraw
    {
        add => PreDrawEvent += value;
        remove => PreDrawEvent -= value;
    }
}

You don't typically need to provide your own custom event accessors. The automatically generated accessors when you declare an event are sufficient for most scenarios. Beginning with C# 14, you can declare partial events. The implementing declaration of a partial event must declare the add and remove handlers.

See also

• Events