c# - -event- can only appear on the left hand side of += or -= -

i have event in loop. trying prevent same method being added event more once. i've implemented add , remove accessors.

however, error stating that:

itemsprocessed can appear on left hand side of += or -=

when try call them, within same class.

itemsprocessed(this, new eventargs()); // produces error  public event eventhandler itemsprocessed {     add     {         itemsprocessed -= value;         itemsprocessed += value;     }     remove     {         itemsprocessed -= value;     } } 

with explicit event, need provide own backing store - either delegate field or eventhandlerlist. current code recursive. try:

private eventhandler itemsprocessed; public event eventhandler itemsprocessed {     add     {         itemsprocessed-= value;         itemsprocessed+= value;     }      remove     {         itemsprocessed-= value;     } } 

then (and noting i'm being little cautious "about turn null" edge-case re threading):

var snapshot = itemsprocessed; if(snapshot != null) snapshot(this, eventargs.empty); 

with more recent c# versions, can simplified:

itemsprocessed?.invoke(this, eventargs.empty);