Adding and Removing Anonymous Event Handler

Question

I was wondering if this actually worked ?

private void RegisterKeyChanged(T item) 
{
    item.OnKeyChanged += (o, k) => ChangeItemKey((T)o, k);
}

private         


        

Answer 1

That won't work I'm afraid, since the two lambda expressions (and delegates) that you declared are actually different objects, and return different references. Hence, the removal of the handler (-=) will always fail.

The common solution to this problem (where you need to remove the handler) is simply to refactor the lamba expression into a proper method. An alternative is to maintain a class variable for the event handler delegate, and add and remove this, though I am personally not a fan of it. (It's more hassle than just creating a normal method, if anything.)