Question

I was wiring up an event to use a lambda which needed to remove itself after triggering. I couldn’t do it by inlining the lambda to the += event (no accessable variable to use to remove the event) so i set up an Action<object, EventArgs> variable and moved the lambda there. The main error was that it could not convert an Action<object, EventArgs> to an EventHandler. I thought lambda expressions were implicitly convertable to event handlers, why doesn’t this work?

Answer 1

Lambdas are implicitly convertible to delegate types with the right shape, but two same-shaped delegate types are not implicitly convertible to one another. Just make the local variable have type EventHandler instead.

EventHandler h = (o, ea) => { ... };
e += h;
...
e -= h;

(in case it helps:

Action<object, EventArgs> a = (o, ea) => { }; 
EventHandler e = a;  // not allowed
EventHandler e2 = (o,ea) => a(o,ea);  // ok

)