Immediate.Cache

Immediate.Cache

Immediate.Cache is a collection of classes that simplify caching responses from Immediate.Handlers handlers.

Installing Immediate.Cache

dotnet add package Immediate.Cache

Using Immediate.Cache

Creating a Cache

Create a class and apply the [CacheFor<>] attribute, targeting a handler. Add a TransformKey method to transform a request into a cache key. For example:

[Handler]
public sealed partial class GetValue
{
	public sealed record Query(int Value);
	public sealed record Response(int Value);

	private ValueTask<Response> HandleAsync(
		Query query,
		CancellationToken _
	) => ValueTask.FromResult(new Response(query.Value));
}

[CacheFor<GetValue>]
public sealed class GetValueCache
{
	protected override string TransformKey(GetValue.Query request) =>
		$"GetValue(query: {request.Value})";
}

In this case, the GetValueCache class will serve as a cache for the GetValue IH handler.

Adding generated caches to the IServiceCollection collection

In your Program.cs, add a call to services.AddXxxCaches(), where Xxx is the application identifier. By default, this is the short form of the assembly name. For example:

• For a project named Web, it will be services.AddWebCaches()
• For a project named Application.Web, it will be services.AddApplicationWebCaches()

However, this name can be overridden using [assembly: ImmediateAssemblyIdentifierAttribute("SomeIdentifier")].

Retrieve Data From the Cache

Using an instance of the GetValueCache class that you have created above, you can simply call:

var response = await cache.GetValue(request, token);

If there is a cached value, it will be returned; otherwise a temporary scope will be used to create the handler and execute it; and the returned value will be stored.

If simultaneous requests are made while the handler is executing, they will wait for the first handler to complete, rather than executing the handler a second/simultaenous time.

Removing Data From the Cache

Using an instance of the GetValueCache class that you have created above, you can remove cached data by calling:

await cache.RemoveValue(request);

If a handler is running based on this request, it will be cancelled, and any callers waiting on the results from this handler will experience a CancellationToken cancellation.

Updating Data In the Cache

Using an instance of the GetValueCache class that you have created above, you can assign cached data by calling:

await cache.SetValue(request, response);

If a handler is running based on this request, it will be cancelled, and any callers waiting on the results from this handler will immediately receive the updated response.