Question

MemoryCache is a thread-safe class, according to this article. But I don’t understand how it will behave in a specific situation. For example I have the code:

static private MemoryCache _cache = MemoryCache.Default;

...

if (_cache.Contains("Test"))
{
    return _cache.Get("Test") as string;
}

1. Can element’s living time expire just after I call Contains() so null value will be returned?
2. Can another thread remove item just after I call Contains() so null value will be returned?

Answer 1

Yes and yes, these are common race conditions. You can avoid them if by simply writing the code as

var test = _cache.Get("Test");
if (test != null) {
    return test as string;
}