36 lines
1.1 KiB
Plaintext
36 lines
1.1 KiB
Plaintext
== Why is this an issue?
|
|
|
|
It is possible to subscribe to events with anonymous delegates, but having done so, it is impossible to unsubscribe from them. That's because the process of subscribing adds the delegate to a list. The process of unsubscribing essentially says: remove _this item_ from the subscription list. But because an anonymous delegate was used in both cases, the unsubscribe attempt tries to remove a different item from the list than was added. The result: ``++NOOP++``.
|
|
|
|
|
|
Instead, save the delegate to a variable and use the variable to subscribe and unsubscribe.
|
|
|
|
|
|
=== Noncompliant code example
|
|
|
|
[source,text]
|
|
----
|
|
listView.PreviewTextInput += (obj,args) =>
|
|
listView_PreviewTextInput(obj,args,listView);
|
|
|
|
// ...
|
|
|
|
listView.PreviewTextInput -= (obj, args) =>
|
|
listView_PreviewTextInput(obj, args, listView); // Noncompliant; this delegate was never subscribed
|
|
----
|
|
|
|
|
|
=== Compliant solution
|
|
|
|
[source,text]
|
|
----
|
|
EventHandler func = (obj,args) => listView_PreviewTextInput(obj,args,listView);
|
|
|
|
listView.PreviewTextInput += func;
|
|
|
|
// ...
|
|
|
|
listView.PreviewTextInput -= func;
|
|
----
|
|
|