Filters are predicates that execute a boolean algebra expression upon an item of a specific type. The abstraction of a filter is defined by the INFilter<T> interface, that has only one method:

bool Filter(T item);

The filter method returns true, if the item passes the filter, otherwise it returns false.

NOV Data Structures implement a large set of commonly used filters that are summarized by the following table:

Filter	Description
Basic Boolean Algebra Filters
NAndFilter<T>	Aggregates two other filters. Returns true if both filters return true, otherwise returns false.
NOrFilter<T>	Aggregates two other filters. Returns true if at least one of the filters return true, otherwise returns false.
NNotFilter<T>	Aggregates a single other filter. Returns true if the aggregated filter returns false, otherwise returns true.
NFalseFilter<T>.Instance	Singleton filter that always returns false.
NTrueFilter<T>.Instance	Singleton filter that always returns true.
Comparison Filters.  (available only when T implements the IComparable<T> interface) All take a comparison Value at construction time.
NEqualsToFilter<T>	Returns true if item.CompareTo(Value) == 0.
NGreaterThanFilter<T>	Returns true if item.CompareTo(Value) > 0.
NGreaterThanOrEqualToFilter<T>	Returns true if item.CompareTo(Value) >= 0.
NLessThanFilter<T>	Returns true if item.CompareTo(Value) < 0.
NLessThanOrEqualToFilter<T>	Returns true if item.CompareTo(Value) <= 0.
Objects Equality Filters. All take a comparison Other object at construction time.
NObjectEqualsFilter<T>	Returns true if item.Equals(Other) == true. Both item and Other can be null.
NReferenceEqualsFilter<T>	Returns true if Object.ReferenceEquals(Other) == true. Both item and Other can be null.
Type Filters. All take a TTargetType as generic argument.
NAsFilter<T, TTargetType>	Aggregates another filter of type INFilter<TTargetType>. Returns true, if the item can be casted to TTargetType and the aggregated filter returns true.
NIsFilter<T, TTargetType>.Instance	Singleton filter, which only passes items, which are instances of TTargetType.
NTypeEqualsFilter<T, TTargetType>.Instance	Singleton filter, which only passes items, whose type is exactly TTargetType.