Szerkesztés

Megosztás a következőn keresztül:

Hashtable.Item[Object] Property

  • Reference

Definition

Namespace:
System.Collections
Assemblies:
mscorlib.dll, System.Collections.NonGeneric.dll
Assembly:
System.Runtime.dll
Assembly:
System.Collections.NonGeneric.dll
Assembly:
System.Runtime.Extensions.dll
Assembly:
mscorlib.dll
Assembly:
netstandard.dll
Source:
Hashtable.cs
Source:
Hashtable.cs
Source:
Hashtable.cs

Gets or sets the value associated with the specified key.

public:
 virtual property System::Object ^ default[System::Object ^] { System::Object ^ get(System::Object ^ key); void set(System::Object ^ key, System::Object ^ value); };
public virtual object this[object key] { get; set; }
public virtual object? this[object key] { get; set; }
member this.Item(obj) : obj with get, set
Default Public Overridable Property Item(key As Object) As Object

Parameters

key
Object

The key whose value to get or set.

Property Value

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

Item[Object]

Exceptions

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.

Remarks

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.

Applies to

See also