When using Cache.Add, is an exception thrown if the key exists already or does it fail silently?
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**I have read everywhere that the Add method fails if it already exists but does it throw an exception or does it fail silently?**

I am writing a multithreaded web application where it should not exist already and it will cause problems if I overwrite the cache, so I can't use the Insert method.

Would this be something I could do:

    try
    {
        HttpContext.Current.Cache.Add("notifications", notifications, null,
          System.Web.Caching.Cache.NoAbsoluteExpiration, TimeSpan.FromHours(8),
          System.Web.Caching.CacheItemPriority.High, null);
    }
    catch
    {
        //do whatever if notifications already exist
    }

Thanks for any answers :)