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Collection(T).Contains Method

Determines whether an element is in the Collection(T).

Namespace:  System.Collections.ObjectModel
Assembly:  mscorlib (in mscorlib.dll)

abstract Contains : 
        item:'T -> bool  
override Contains : 
        item:'T -> bool


Type: T

The object to locate in the Collection(T). The value can be a null reference (Nothing in Visual Basic) for reference types.

Return Value

Type: System.Boolean
true if item is found in the Collection(T); otherwise, false.



If the Collection(T) object is created using the default 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.

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

XNA Framework

Supported in: 3.0, 2.0, 1.0

Portable Class Library

Supported in: Portable Class Library

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8
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