title: ObjectForKey always returns null xamarin.ios
body: <p>I have tried to set string into the cache using NSCache in Xamarin.iOS setting id done without problem, but when tries to get this cached value always return null, any one can help, please?</p>
  
  <pre><code>/*set*/
  public static void AddCachedString(NSString key, NSString Value)
  {
      cacheProvider.SetObjectforKey(key, Value);
  }
  
  /*get*/
  public static NSString GetCachedString(NSString key)
  {
       return (NSString)cacheProvider.ObjectForKey(key);
  }
  </code></pre>