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Hashtable.ContainsKey Method

Determines whether the Hashtable contains a specific key.

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

abstract ContainsKey : 
        key:Object -> bool  
override ContainsKey : 
        key:Object -> bool

Parameters

key
Type: System.Object

The key to locate in the Hashtable.

Return Value

Type: System.Boolean
true if the Hashtable contains an element with the specified key; otherwise, false.

ExceptionCondition
ArgumentNullException

key is a null reference (Nothing in Visual Basic).

This method behaves exactly as Contains.

This method is an O(1) operation.

Starting with the .NET Framework 2.0, this method uses the collection’s objects’ Equals and CompareTo methods on item to determine whether item exists. In the earlier versions of the .NET Framework, this determination was made by using the Equals and CompareTo methods of the item parameter on the objects in the collection.

The following example shows how to determine whether the Hashtable contains a specific element.

No code example is currently available or this language may not be supported.

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

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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