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Hashtable.Item Property

Gets or sets the value associated with the specified key.

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

public virtual Object this[
	Object key
] { get; set; }

Parameters

key
Type: System.Object

The key whose value to get or set.

Property Value

Type: System.Object
The value associated with the specified key. If the specified key is not found, attempting to get it returns null, and attempting to set it creates a new element using the specified key.

Implements

IDictionary.Item

ExceptionCondition
ArgumentNullException

key is null.

NotSupportedException

The property is set and the Hashtable is read-only.

-or-

The property is set, key does not exist in the collection, and the Hashtable has a fixed size.

This property provides the ability to access a specific element in the collection by using the following syntax: myCollection[key].

You can also use the Item property to add new elements by setting the value of a key that does not exist in the Hashtable; for example, myCollection["myNonexistentKey"] = myValue. However, if the specified key already exists in the Hashtable, setting the Item property overwrites the old value. In contrast, the Add method does not modify existing elements.

A key cannot be null, but a value can be. To distinguish between null that is returned because the specified key is not found and null that is returned because the value of the specified key is null, use the Contains method or the ContainsKey method to determine if the key exists in the list.

Retrieving the value of this property is an O(1) operation; setting the property is also an O(1) operation.

The C# language uses the this keyword to define the indexers instead of implementing the Item property. Visual Basic implements Item as a default property, which provides the same indexing functionality.

.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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