Collection<T>.Contains(T) Method


Determines whether an element is in the Collection<T>.

 virtual bool Contains(T item);
public bool Contains (T item);
abstract member Contains : 'T -> bool
override this.Contains : 'T -> bool
Public Function Contains (item As T) As Boolean



The object to locate in the Collection<T>. The value can be null for reference types.


true if item is found in the Collection<T>; otherwise, false.



If the Collection<T> object is created using the parameterless constructor, this method determines equality using the default equality comparer EqualityComparer<T>.Default for T, the type of values in the list. If type T does not implement the IEquatable<T> interface, the Equals method is used.

If the Collection object is created by passing an IList<T> object to the constructor, the Contains method will be determined by the IEqualityComparer<T> interface used by that IList<T> object.

This method performs a linear search; therefore, the average execution time is proportional to Count. That is, this method is an O(n) operation, where n is Count.

Applies to

See also