/// <summary>
/// Attempts to get a value from cache.
/// If it is found in cache, return true, and the value.
/// If it is not found in cache, return false, and use the valueFactory callback to generate and return the value.
/// </summary>
/// <param name="key">The key.</param>
/// <param name="value">The value.</param>
/// <param name="valueFactory">A callback that can create the value.</param>
/// <returns>
/// True if the value came from cache, otherwise false.
/// </returns>
/// <exception cref="System.ArgumentNullException">valueFactory</exception>
public bool TryGetOrAdd(TKey key, out TValue value, Func <TKey, TValue> valueFactory)
{
if (valueFactory == null)
{
throw new ArgumentNullException(nameof(valueFactory));
}
Func <TKey, TimeoutEntry> callback = key1 =>
{
TValue newValue = valueFactory(key1);
var newEntry = TimeoutEntry.Create(newValue);
return(newEntry);
};
TimeoutEntry entry = null;
bool isValid = false;
bool fromCache = false;
while (!isValid)
{
fromCache = _cache.TryGetOrAdd(key, out entry, callback);
/////
// Check time stamp
/////
if (fromCache)
{
isValid = IsValid(entry);
if (!isValid)
{
Remove(key);
}
}
else
{
isValid = true;
}
}
value = entry.Value;
return(fromCache);
}
/// <summary>
/// Adds or updates the specified key/value pair.
/// </summary>
/// <param name="key">The key.</param>
/// <param name="value">The value.</param>
/// <returns>
/// True if the specified key/value pair was added;
/// False if the specified key/value pair was updated.
/// </returns>
public bool Add(TKey key, TValue value)
{
return(_cache.Add(key, TimeoutEntry.Create(value)));
}