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SortedDictionary.System.Collections.IDictionary.Contains Method

Determines whether the IDictionary contains an element with the specified key.

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

bool IDictionary.Contains (
	Object key
Not applicable.



The key to locate in the IDictionary.

Return Value

true if the IDictionary contains an element with the key; otherwise, false.

Exception typeCondition


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

This method returns false if key is of a type that is not assignable to the key type TKey of the SortedDictionary.

This method is an O(log n) operation, where n is Count.

The following code example shows how to use the System.Collections.IDictionary.Contains method of the System.Collections.IDictionary interface with a SortedDictionary. The example demonstrates that the method returns false if a key of the wrong data type is supplied.

The code example is part of a larger example, including output, provided for the System.Collections.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");


        // Contains can be used to test keys before inserting 
        // them.
        if (!openWith.Contains("ht"))
            openWith.Add("ht", "hypertrm.exe");
            Console.WriteLine("Value added for key = \"ht\": {0}", 

        // IDictionary.Contains returns false if the wrong data
        // type is supplied.
        Console.WriteLine("openWith.Contains(29.7) returns {0}",



Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, 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