Cache policy gives unhelpful exception on sync/async config/execution mismatch

I am following the samples to implement cache but I’m getting an exception during the call:

This is the policiy definition:

var cachePolicy = Policy.Cache(new MemoryCacheProvider(MemoryCache.Default), TimeSpan.FromMinutes(5))

Then this is the call:

return cachePolicy.ExecuteAsync(async () => await _webService.someMethodAsync());

And this is the error it throws:

Value cannot be null. Parameter name: nonGenericCacheProvider" at Polly.Caching.GenericCacheProviderAsync'1..ctor(IAsyncCacheProvider nonGenericCacheProvider)

What am I missing? I think this pretty much matches the samples offered in the Readme.md, but still no idea how to get rid of that exception.

BTW: the ExecuteAsync overload to set Context and set the operationKey shows as deprecated, something not mentioned in documentation.

[reisenberger]

@CesarD For asynchronous executions using ExecuteAsync(...), the policy must be defined as an asynchronous policy, thus:

var cachePolicy = Policy.CacheAsync(new MemoryCacheProvider(MemoryCache.Default), TimeSpan.FromMinutes(5));

All policies should give a helpful exception message explaining that, if sync/async are mixed incorrectly, but this case has escaped that. I’ll fix to make sure it gives a helpful exception.

Thanks for spotting the deprecated overload quoted in the cache documentation: it’ll be corrected in both the readme and wiki.

[reisenberger]

@CesarD Thanks for the feedback. Extra clarification added:

• readme
• wiki