This documentation is archived and is not being maintained.

SortedDictionary<TKey, TValue>.Add Method

Adds an element with the specified key and value into the SortedDictionary<TKey, TValue>.

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

public void Add(
	TKey key,
	TValue value


Type: TKey

The key of the element to add.

Type: TValue

The value of the element to add. The value can be null for reference types.


IDictionary<TKey, TValue>.Add(TKey, TValue)


key is null.


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

You can also use the Item property to add new elements by setting the value of a key that does not exist in the SortedDictionary<TKey, TValue>; for example, myCollection["myNonexistentKey"] = myValue (in Visual Basic, myCollection("myNonexistantKey") = myValue). However, if the specified key already exists in the SortedDictionary<TKey, TValue>, setting the Item property overwrites the old value. In contrast, the Add method throws an exception if an element with the specified key already exists.

A key cannot be null, but a value can be, if the value type TValue is a reference type.

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

The following code example creates an empty SortedDictionary<TKey, TValue> of strings with string keys and uses the Add method to add some elements. The example demonstrates that the Add method throws an ArgumentException when attempting to add a duplicate key.

This code example is part of a larger example provided for the SortedDictionary<TKey, TValue> class.

// Create a new sorted dictionary of strings, with string 
// keys.
SortedDictionary<string, string> openWith = 
    new SortedDictionary<string, string>();

// Add some elements to the dictionary. There are no  
// duplicate keys, but some of the values are duplicates.
openWith.Add("txt", "notepad.exe");
openWith.Add("bmp", "paint.exe");
openWith.Add("dib", "paint.exe");
openWith.Add("rtf", "wordpad.exe");

// The Add method throws an exception if the new key is  
// already in the dictionary. 
    openWith.Add("txt", "winword.exe");
catch (ArgumentException)
    Console.WriteLine("An element with Key = \"txt\" already exists.");

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0