public async Task <T> GetOrSetAsync <T>(string key, Func <Task <T> > expression, TimeSpan expiresIn) where T : class
{
var found = Get <T>(key);
if (found != null)
{
return(await TaskExtension.FromResultEx(found));
}
var executed = await expression();
_cache.Set(key, executed, DateTime.Now + expiresIn);
return(await TaskExtension.FromResultEx(executed));
}