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SortedDictionary<TKey, TValue>.IDictionary.Keys Property

Gets an ICollection containing the keys of the IDictionary.

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

ICollection IDictionary.Keys { get; }

Property Value

Type: System.Collections.ICollection
An ICollection containing the keys of the IDictionary.

Implements

IDictionary.Keys

The keys in the returned ICollection are sorted according to the Comparer property and are guaranteed to be in the same order as the corresponding values in the ICollection returned by the Values property.

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

The following code example shows how to use the IDictionary<TKey, TValue>.Keys property of the System.Collections.IDictionary interface with a SortedDictionary<TKey, TValue>, to list the keys in the dictionary. The example also shows how to enumerate the key/value pairs in the dictionary; note that the enumerator for the System.Collections.IDictionary interface returns DictionaryEntry objects rather than KeyValuePair<TKey, TValue> objects.

The code example is part of a larger example, including output, provided for the IDictionary.Add method.

using System;
using System.Collections;
using System.Collections.Generic;

public class Example
{
    public static void Main()
    {
        // Create a new sorted dictionary of strings, with string keys, 
        // and access it using the IDictionary interface. 
        //
        IDictionary openWith = new SortedDictionary<string, string>();

        // Add some elements to the dictionary. There are no  
        // duplicate keys, but some of the values are duplicates. 
        // IDictionary.Add throws an exception if incorrect types 
        // are supplied for key or value.
        openWith.Add("txt", "notepad.exe");
        openWith.Add("bmp", "paint.exe");
        openWith.Add("dib", "paint.exe");
        openWith.Add("rtf", "wordpad.exe");


...


// To get the keys alone, use the Keys property.
icoll = openWith.Keys;

// The elements of the collection are strongly typed 
// with the type that was specified for dictionary keys, 
// even though the ICollection interface is not strongly 
// typed.
Console.WriteLine();
foreach( string s in icoll )
{
    Console.WriteLine("Key = {0}", s);
}


...


// When you use foreach to enumerate dictionary elements 
// with the IDictionary interface, the elements are retrieved 
// as DictionaryEntry objects instead of KeyValuePair objects.
Console.WriteLine();
foreach( DictionaryEntry de in openWith )
{
    Console.WriteLine("Key = {0}, Value = {1}", 
        de.Key, de.Value);
}


...


    }
}

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1

Windows Phone 8.1, Windows Phone 8, 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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