C# 0 The Complete Reference

The SortedDictionary Class

The

SortedDictionary

 class stores key/value pairs and is similar to 

Dictionary

TV>

 except that it is sorted by key. 

SortedDictionary

 implements 

IDictionary

,

IDictionary

,

ICollection

,

 ICollection>

,

IEnumerable

,

and

IEnumerable>

.

SortedDictionary

 provides the 

following constructors:

public SortedDictionary( )

public SortedDictionary(IDictionary 

dict

)

public SortedDictionary(IComparer 

comp

)

public SortedDictionary(IDictionary 

dict

, IComparer 

comp

)

The first constructor creates an empty dictionary. The second creates a dictionary that 

contains the same elements as those in 

dict.

 The third lets you specify the 

IComparer

 that 

the dictionary will use for sorting, and the fourth lets you initialize the dictionary and 

specify the 

IComparer

.

SortedDictionary

 defines several methods. A sampling is shown in Table 24-17.

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In addition to the properties defined by the interfaces that it implements, 

SortedDictionary

 defines the following properties:

Property

Description

public IComparer Comparer { get; }

Obtains the comparer for the invoking 

dictionar y.

public

    Sor tedDictionar y.KeyCollection

         Keys { get; }

Obtains a collection of the keys. 

public

    Sor tedDictionar y.ValueCollection

          Values { get; }

Obtains a collection of the values. 

Notice that the keys and values contained within the collection are available as separate lists 

through the 

Keys

 and 

Values

 properties. The types

SortedDictionary.KeyCollection

SortedDictionary.ValueCollection

are collections that implement both the generic and non-generic forms of 

ICollection

 and 

IEnumerable

.

SortedDictionary

 defines the following indexer (which is specified by 

IDictionary

):

public TV this[TK 

key

] { get; set; }

You can use this indexer to get or set the value of an element. You can also use it to add a 

new element to the collection. Notice that the “index” is not actually an index, but rather the 

key of the item.

Method

Description

public void Add(TK 

k

, TV 

v

)

Adds the key/value pair specified by 

k

 and 

v

 to the dictionar y. If 

k

 is already in the 

dictionar y, then its value is unchanged and 

an

ArgumentException

 is thrown.

public bool ContainsKey(TK 

k

)

Returns true if 

k

 is a key in the invoking 

dictionar y. Returns false other wise.

public bool ContainsValue(TV 

v

)

Returns true if 

v

 is a value in the invoking 

dictionar y. Returns false other wise.

public Sor tedDictionar y.Enumerator

     GetEnumerator( )

Returns an enumerator for the invoking 

dictionar y. 

public bool Remove(TK 

k

)

Removes 

k

 from the dictionar y. Returns true 

if successful. Returns false if

k

 was not in 

the dictionar y.

T

ABLE

 24-17 

A Sampling of Methods Defi ned by 

SortedDictionary

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