See blog article for more background details.
Grab the Nuget package called Strathweb.AsyncExpiringLazy. Built with .NET Standard 1.1 and compatible with:
- .NET 4.5+
- .NET Core
- Xamarin
- Mono
- Universal Windows Platform
Latest version:
The code sample shows creating a lazy epxiring value and letting it get recreated.
var testInstance = new AsyncExpiringLazy<TokenResponse>(async metadata =>
{
await Task.Delay(1000);
return new ExpirationMetadata<TokenResponse>
{
Result = new TokenResponse
{
AccessToken = Guid.NewGuid().ToString()
}, ValidUntil = DateTimeOffset.UtcNow.AddSeconds(2)
};
});
// 1. check if value is created - shouldn't
Assert.False(await testInstance.IsValueCreated());
// 2. fetch lazy expiring value
var token = await testInstance.Value();
// 3a. verify it is created now
Assert.True(await testInstance.IsValueCreated());
// 3b. verify it is not null
Assert.NotNull(token.AccessToken);
// 4. fetch the value again. Since it's lifetime is 2 seconds, it should be still the same
var token2 = await testInstance.Value();
Assert.Same(token, token2);
// 5. sleep for 2 seconds to let the value expire
await Task.Delay(2000);
// 6. fetch again
var token3 = await testInstance.Value();
// 7. verify we now have a new (recreated) value - as the previous one expired
Assert.NotSame(token2, token3);
// 8. invalidate the value manually before it has a chance to expire
await testInstance.Invalidate();
// 9. check if value is created - shouldn't anymore
Assert.False(await testInstance.IsValueCreated());