Keys Property

Dictionary.Keys Property

Gets a collection containing the keys in the Dictionary.

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

public KeyCollection Keys { get; }
/** @property */
public KeyCollection get_Keys ()

public function get Keys () : KeyCollection

Not applicable.

Property Value

A Dictionary.KeyCollection containing the keys in the Dictionary.

The order of the keys in the Dictionary.KeyCollection is unspecified, but it is the same order as the associated values in the Dictionary.ValueCollection returned by the Values property.

The returned Dictionary.KeyCollection is not a static copy; instead, the Dictionary.KeyCollection refers back to the keys in the original Dictionary. Therefore, changes to the Dictionary continue to be reflected in the Dictionary.KeyCollection.

Getting the value of this property is an O(1) operation.

The following code example shows how to enumerate the keys in the dictionary using the Keys property, and how to enumerate the keys and values in the dictionary.

This code is part of a larger example that can be compiled and executed. See Dictionary.

    // To get the keys alone, use the Keys property.
    Dictionary<string, string>.KeyCollection keyColl =

    // The elements of the KeyCollection are strongly typed
    // with the type that was specified for dictionary keys.
    foreach( string s in keyColl )
        Console.WriteLine("Key = {0}", s);


    // When you use foreach to enumerate dictionary elements,
    // the elements are retrieved as KeyValuePair objects.
    foreach( KeyValuePair<string, string> kvp in openWith )
        Console.WriteLine("Key = {0}, Value = {1}", 
            kvp.Key, kvp.Value);

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

.NET Compact Framework

Supported in: 2.0

XNA Framework

Supported in: 1.0

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