Does mvvm light v3 unregister work properly?

Is there a problem with the MvvM-Light v3 unregister?

I am registering like this:

 Messen开发者_StackOverflowger.Default.Register<DialogResponse>(this,
                                            MessageTypesUI.YesNoQueryResponse,
                                            AnswerResponse);

Then in "AnswerResponse"

 Messenger.Default.Unregister<DialogResponse>(MessageTypesUI.YesNoQueryResponse);

Both methods execute, and AnswerResponse is called, but the second time it is called twice and the third time thrice, etc.

It acts as if my "Unregister" is being ignored.

I tried it both with Unregister() and plain old Unregister()

There was something in the release notes for V4 that made me suspect a problem with the version 3 unregister...

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You should modify the call to Unregister to pass in the recipient object, not the message type:

Messenger.Default.Unregister<DialogResponse>(this);

If you look at the MVVM Light code for the messenger all unregister actions use the recipient - as internally the recipient is used for identifying which message handlers will be removed. The most basic method is Unregister(recipient), which de-registers all actions for a given recipient. All additional parameters allow for a more fine grained approach.

If you have multiple actions handling the same message type and you want to unregister only one of them you can use

Messenger.Unregister<DialogMessage>(recipient, action);

to only remove one of the actions.

Edit

The MVVM Light release notes for V. 4 indicate the following changes to the Messenger:

1. Missing methods where added to. The IMessenger interface.
2. An additional Unregister method allowing to use tokens for filtering was added.
3. The Messenger.CleanupList method was made thread safe.