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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; }
/** @property */
public Object get_Item (Object key)

/** @property */
public void set_Item (Object key, Object value)

Not applicable.

Parameters

key

The key whose value to get or set.

Property Value

The value associated with the specified key. If the specified key is not found, attempting to get it returns a null reference (Nothing in Visual Basic), and attempting to set it creates a new element using the specified key.

Exception typeCondition

ArgumentNullException

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

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 a null reference (Nothing in Visual Basic), but a value can be. To distinguish between a null reference (Nothing in Visual Basic) that is returned because the specified key is not found and a null reference (Nothing in Visual Basic) that is returned because the value of the specified key is a null reference (Nothing in Visual Basic), 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.

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0

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