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Dictionary.Dictionary(Generic IDictionary) Constructor

Initializes a new instance of the Dictionary class that contains elements copied from the specified IDictionary and uses the default equality comparer for the key type.

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

public Dictionary (
	IDictionary<TKey,TValue> dictionary
public Dictionary (
	IDictionary<TKey,TValue> dictionary
public function Dictionary (
	dictionary : IDictionary<TKey,TValue>
Not applicable.



The IDictionary whose elements are copied to the new Dictionary.

Exception typeCondition


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


dictionary contains one or more duplicate keys.

Every key in a Dictionary must be unique according to the default equality comparer; likewise, every key in the source dictionary must also be unique according to the default equality comparer.

The initial capacity of the new Dictionary is large enough to contain all the elements in dictionary.

Dictionary requires an equality implementation to determine whether keys are equal. This constructor uses the default generic equality comparer, EqualityComparer.Default. If type TKey implements the System.IEquatable generic interface, the default equality comparer uses that implementation. Alternatively, you can specify an implementation of the IEqualityComparer generic interface by using a constructor that accepts a comparer parameter.

This constructor is an O(n) operation, where n is the number of elements in dictionary.

The following code example shows how to use the Dictionary(Generic IEqualityComparer) constructor to initialize a Dictionary with sorted content from another dictionary. The code example creates a SortedDictionary and populates it with data in random order, then passes the SortedDictionary to the Dictionary(Generic IEqualityComparer) constructor, creating a Dictionary that is sorted. This is useful if you need to build a sorted dictionary that at some point becomes static; copying the data from a SortedDictionary to a Dictionary improves retrieval speed.

using System;
using System.Collections.Generic;

public class Example
    public static void Main()
        // Create a new sorted dictionary of strings, with string 
        // keys.
        SortedDictionary<string, string> openWith = 
            new SortedDictionary<string, string>();
        // Add some elements to the dictionary. 
        openWith.Add("txt", "notepad.exe");
        openWith.Add("bmp", "paint.exe");
        openWith.Add("dib", "paint.exe");
        openWith.Add("rtf", "wordpad.exe");
        // Create a Dictionary of strings with string keys, and 
        // initialize it with the contents of the sorted dictionary.
        Dictionary<string, string> copy = 
            new Dictionary<string, string>(openWith);

        // List the contents of the copy.
        foreach( KeyValuePair<string, string> kvp in copy )
            Console.WriteLine("Key = {0}, Value = {1}", 
               kvp.Key, kvp.Value);

/* This code example produces the following output:

Key = bmp, Value = paint.exe
Key = dib, Value = paint.exe
Key = rtf, Value = wordpad.exe
Key = txt, Value = notepad.exe

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