/// <summary>
/// Creates an instance of ContentPresenterVisualHelper for the given ContentPresenter and ChildName, if necessary.
/// Or returns an existing one from cache, if available.
/// </summary>
public static ContentPresenterVisualHelper GetInstance(ContentPresenter ContentPresenter, string ChildName)
{
string key = CreateKey(ContentPresenter, ChildName);
var cachedObj = Cache.Get(key) as ContentPresenterVisualHelper;
if (cachedObj != null)
{
return(cachedObj);
}
lock (CacheLock)
{
cachedObj = Cache.Get(key) as ContentPresenterVisualHelper;
if (cachedObj != null)
{
return(cachedObj);
}
var obj = new ContentPresenterVisualHelper(ContentPresenter, ChildName);
var cacheItem = new CacheItem(key, obj);
var expiration = DateTimeOffset.Now + TimeSpan.FromSeconds(60);
var policy = new CacheItemPolicy {
AbsoluteExpiration = expiration
};
Cache.Set(cacheItem, policy);
return(obj);
}
}
/// <param name="parameter">
/// 1. Can be null/empty, in which case the first Visual Child of the ContentPresenter is returned by the Helper
/// 2. Can be a string, in which case the ContentPresenter's child with the given name is returned
/// </param>
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
if (value == null)
{
return(null);
}
ContentPresenter cp = value as ContentPresenter;
if (cp == null)
{
throw new InvalidOperationException(String.Format("value must be of type ContentPresenter, but was {0}", value.GetType().FullName));
}
return(ContentPresenterVisualHelper.GetInstance(cp, parameter as string));
}
