c# - why introduce a temp variable? -

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this question has answer here:

i saw lot of following usage of event handler. why assign handler local variable , use local variable?

event eventhandler propertychanged;  private void raisepropertychanged(string propertyname) {     var temp = propertychanged;     if (temp != null)         temp(this, new propertychangedeventargs(propertyname));     // why not "if (propertychanged != null) propertychanged(...)"  }

the temporary variable ensures thread safety, because between check , actual call other thread may unsubscribe event result in nullreferenceexception.

eric lippert has a great article on this


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