The instance of IConfigurationMonitor is injected into the IndexModel. The Index page offers the user control over configuration monitoring. AddJsonFile($"appsettings.") Īn instance ConfigurationMonitor is registered as a service in Startup.ConfigureServices: services.AddSingleton()
This setting appears in the Host convenience method CreateDefaultBuilder: config.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
reloadOnChange indicates if configuration should be reloaded on file changes. These files are configured using the AddJsonFile(IConfigurationBuilder, String, Boolean, Boolean) extension method on ConfigurationBuilder that accepts a reloadOnChange parameter. Each instance returns an IChangeToken to register a change notification callback for tracking options changes.īy default, ASP.NET Core templates use JSON configuration files ( appsettings.json,, and ) to load app configuration settings. For TOptions changes, the default OptionsMonitor implementation of IOptionsMonitor has an overload that accepts one or more IOptionsChangeTokenSource instances.IChangeToken tokens can be added to cache entries to trigger cache evictions on change.For monitoring changes to files, IFileProvider's Watch method creates an IChangeToken for the specified files or folder to watch.Example uses of change tokens in ASP.NET CoreĬhange tokens are used in prominent areas of ASP.NET Core to monitor for changes to objects: Calling Dispose stops the token from listening for further changes and releases the token's resources. The ChangeToken.OnChange(Func, Action, TState) overload takes an additional TState parameter that's passed into the token consumer Action. Action is called when the token changes.The ChangeToken.OnChange(Func, Action) method registers an Action to call whenever the token changes: The NuGet package is implicitly provided to the ASP.NET Core apps. ChangeToken classĬhangeToken is a static class used to propagate notifications that a change has occurred. HasChanged must be set before the callback is invoked.
The IChangeToken interface includes the RegisterChangeCallback(Action, Object) method, which registers a callback that's invoked when the token has changed. HasChanged receives a value that indicates if a change has occurred.It's also possible for a token to never be cancelled if no changes occur or the underlying change listener is disposed or disabled. If ActiveChangedCallbacks is set to false, a callback is never called, and the app must poll HasChanged for changes. ActiveChangeCallbacks indicate if the token proactively raises callbacks.IChangeToken propagates notifications that a change has occurred.
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View or download sample code ( how to download) IChangeToken interface A change token is a general-purpose, low-level building block used to track state changes.
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