what is the meaning of “ += ( s, e )” in the code?

Question

What is exactly the += ( s, e ) in the code?

example:

this.currentOperation.Completed += ( s, e ) => this.CurrentOperationChanged();

Answer 1

It is a shorthand for an event handler. s --> object sender and e --> some type of EventArgs.

It can also be rewrriten as:

public void HandlerFunction(object sender, EventArgs e)
{
   this.loaded = true;
}