ConcurrentCollections Represents a thread-safe hash-based unique collection. The type of the items in the collection. All public members of are thread-safe and may be used concurrently from multiple threads. Gets the number of items contained in the . The number of items contained in the . Count has snapshot semantics and represents the number of items in the at the moment when Count was accessed. Gets a value that indicates whether the is empty. true if the is empty; otherwise, false. Initializes a new instance of the class that is empty, has the default concurrency level, has the default initial capacity, and uses the default comparer for the item type. Initializes a new instance of the class that is empty, has the specified concurrency level and capacity, and uses the default comparer for the item type. The estimated number of threads that will update the concurrently. The initial number of elements that the can contain. is less than 1. is less than 0. Initializes a new instance of the class that contains elements copied from the specified , has the default concurrency level, has the default initial capacity, and uses the default comparer for the item type. The whose elements are copied to the new . is a null reference. Initializes a new instance of the class that is empty, has the specified concurrency level and capacity, and uses the specified . The implementation to use when comparing items. Initializes a new instance of the class that contains elements copied from the specified , has the default concurrency level, has the default initial capacity, and uses the specified . The whose elements are copied to the new . The implementation to use when comparing items. is a null reference (Nothing in Visual Basic). Initializes a new instance of the class that contains elements copied from the specified , has the specified concurrency level, has the specified initial capacity, and uses the specified . The estimated number of threads that will update the concurrently. The whose elements are copied to the new . The implementation to use when comparing items. is a null reference. is less than 1. Initializes a new instance of the class that is empty, has the specified concurrency level, has the specified initial capacity, and uses the specified . The estimated number of threads that will update the concurrently. The initial number of elements that the can contain. The implementation to use when comparing items. is less than 1. -or- is less than 0. Adds the specified item to the . The item to add. true if the items was added to the successfully; false if it already exists. The contains too many items. Removes all items from the . Determines whether the contains the specified item. The item to locate in the . true if the contains the item; otherwise, false. Attempts to remove the item from the . The item to remove. true if an item was removed successfully; otherwise, false. Returns an enumerator that iterates through the . An enumerator for the . The enumerator returned from the collection is safe to use concurrently with reads and writes to the collection, however it does not represent a moment-in-time snapshot of the collection. The contents exposed through the enumerator may contain modifications made to the collection after was called.