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Dictionary<TKey, TValue>.ICollection<KeyValuePair<TKey, TValue>>.Add Method

Adds the specified value to the ICollection<T> with the specified key.

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

void ICollection<KeyValuePair<TKey, TValue>>.Add(
	KeyValuePair<TKey, TValue> keyValuePair


Type: System.Collections.Generic.KeyValuePair<TKey, TValue>

The KeyValuePair<TKey, TValue> structure representing the key and value to add to the Dictionary<TKey, TValue>.




The key of keyValuePair is null.


An element with the same key already exists in the Dictionary<TKey, TValue>.

If Count is less than the capacity, this method approaches an O(1) operation. If the capacity needs to be increased to accommodate the new element, this method becomes an O(n) operation, where n is Count.

The following example shows how to use the ICollection<KeyValuePair<TKey, TValue>>.Add, ICollection<KeyValuePair<TKey, TValue>>.Contains, ICollection<KeyValuePair<TKey, TValue>>.CopyTo, and ICollection<KeyValuePair<TKey, TValue>>.Remove methods of the System.Collections.Generic.ICollection<T> generic interface to manipulate a Dictionary<TKey, TValue> object.

using System;
using System.Collections.Generic;

public class Example
    public static void Main()
        // Create a new dictionary of strings, with string keys, and 
        // access it through the generic ICollection interface. The 
        // generic ICollection interface views the dictionary as a 
        // collection of KeyValuePair objects with the same type 
        // arguments as the dictionary. 
        ICollection<KeyValuePair<String, String>> openWith =
            new Dictionary<String, String>();

        // Add some elements to the dictionary. When elements are  
        // added through the ICollection<T> interface, the keys 
        // and values must be wrapped in KeyValuePair objects. 
        openWith.Add(new KeyValuePair<String,String>("txt", "notepad.exe"));
        openWith.Add(new KeyValuePair<String,String>("bmp", "paint.exe"));
        openWith.Add(new KeyValuePair<String,String>("dib", "paint.exe"));
        openWith.Add(new KeyValuePair<String,String>("rtf", "wordpad.exe"));

        foreach( KeyValuePair<string, string> element in openWith )
            Console.WriteLine("{0}, {1}", element.Key, element.Value);

        // The Contains method also takes a KeyValuePair object. 
            "\nContains(KeyValuePair(\"txt\", \"notepad.exe\")): {0}", 
            openWith.Contains(new KeyValuePair<String,String>("txt", "notepad.exe")));

        // The Remove method takes a KeyValuePair object.) 
        // Use the Remove method to remove a key/value pair.
        Console.WriteLine("\nRemove(new KeyValuePair(\"dib\", \"paint.exe\"))");
        openWith.Remove(new KeyValuePair<String,String>("dib", "paint.exe"));

        foreach( KeyValuePair<string, string> element in openWith )
            Console.WriteLine("{0}, {1}", element.Key, element.Value);

        // Create an array of KeyValuePair objects and copy the  
        // contents of the dictionary to it.  
        KeyValuePair<string, string>[] copy = 
            new KeyValuePair<string, string>[openWith.Count];
        openWith.CopyTo(copy, 0);

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

/* This code example produces the following output:

txt, notepad.exe
bmp, paint.exe
dib, paint.exe
rtf, wordpad.exe

Contains(KeyValuePair("txt", "notepad.exe")): True

Remove(new KeyValuePair("dib", "paint.exe"))

txt, notepad.exe
bmp, paint.exe
rtf, wordpad.exe

txt, notepad.exe
bmp, paint.exe
rtf, wordpad.exe

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

XNA Framework

Supported in: 3.0, 2.0, 1.0

.NET for Windows Phone apps

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

Portable Class Library

Supported in: Portable Class Library
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