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Dictionary<TKey, TValue>.IDictionary.Contains Method

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

Namespace:  System.Collections.Generic
Assembly:  mscorlib (in mscorlib.dll)
bool IDictionary.Contains(
	Object key
)

Parameters

key
Type: System.Object
The key to locate in the IDictionary.

Return Value

Type: System.Boolean
true if the IDictionary contains an element with the specified key; otherwise, false.

Implements

IDictionary.Contains(Object)
ExceptionCondition
ArgumentNullException

key is null.

This method returns false if key is of a type that is not assignable to the key type TKey of the Dictionary<TKey, TValue>.

This method approaches an O(1) operation.

The following code example shows how to use the IDictionary.Contains method of the System.Collections.IDictionary interface with a Dictionary<TKey, TValue>. 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 IDictionary.Add method.


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

public class Example
{
    public static void Main()
    {
        // Create a new dictionary of strings, with string keys,
        // and access it using the IDictionary interface.
        //
        IDictionary openWith = new Dictionary<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}", 
        openWith["ht"]);
}

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


...


    }
}


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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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