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IReadOnlyDictionary<TKey, TValue>.ContainsKey Method

.NET Framework 4.5

Determines whether the read-only dictionary contains an element that has the specified key.

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

bool ContainsKey(
	TKey key


Type: TKey

The key to locate.

Return Value

Type: System.Boolean
true if the read-only dictionary contains an element that has the specified key; otherwise, false.


key is null.

Implementations can vary in how they determine the equality of objects; for example, the class that implements IReadOnlyDictionary<TKey, TValue> might use the Comparer<T>.Default property, or it might implement the IComparer<T> method.

Implementations can vary in whether they allow key to be null.

.NET Framework

Supported in: 4.5

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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