Xamarin.Forms.Core 1.0.0.0 1.1.0.0 1.2.0.0 1.3.0.0 1.4.0.0 1.5.0.0 2.0.0.0 System.Delegate System.Void The collection that was passed to . The context or lock object that was passed to . An action that reads or modifies . A value that tells whether write access is required by .

Delegate for callback in .

Application developers implement a method and pass it to the method to enable correct multithreaded access to . After synchronization is enabled, the Xamarin.Forms framework passes to the application developer's implementation of each time that the framework needs to modify the collection in a multithreaded environment. The application developer's implementation should decide, based on the object (which may be merely a locking object or the object on which the collection lives) and the value of the parameter, whether or not to lock while calling .