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Dictionary<TKey, TValue>.Keys Property

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Gets a collection containing the keys in the Dictionary<TKey, TValue>.

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

Syntax

'Declaration
Public ReadOnly Property Keys As Dictionary<(Of <(<'TKey, TValue>)>)>..::..KeyCollection

public Dictionary<(Of <(<'TKey, TValue>)>)>..::..KeyCollection Keys { get; }

Remarks

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

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

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

Examples

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<TKey, TValue>.

' To get the keys alone, use the Keys property.
Dim keyColl As  _
    Dictionary(Of String, String).KeyCollection = _
    openWith.Keys

' The elements of the KeyCollection are strongly typed
' with the type that was specified for dictionary keys.
outputBlock.Text &= vbCrLf
For Each s As String In keyColl
   outputBlock.Text &= String.Format("Key = {0}", s) & vbCrLf
Next s


...


' When you use foreach to enumerate dictionary elements,
' the elements are retrieved as KeyValuePair objects.
outputBlock.Text &= vbCrLf
For Each kvp As KeyValuePair(Of String, String) In openWith
   outputBlock.Text &= String.Format("Key = {0}, Value = {1}", _
       kvp.Key, kvp.Value) & vbCrLf
Next kvp

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

// The elements of the KeyCollection are strongly typed
// with the type that was specified for dictionary keys.
outputBlock.Text += "\n";
foreach (string s in keyColl)
{
   outputBlock.Text += String.Format("Key = {0}", s) + "\n";
}


...


// When you use foreach to enumerate dictionary elements,
// the elements are retrieved as KeyValuePair objects.
outputBlock.Text += "\n";
foreach (KeyValuePair<string, string> kvp in openWith)
{
   outputBlock.Text += String.Format("Key = {0}, Value = {1}",
       kvp.Key, kvp.Value) + "\n";
}

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.