C# 0 The Complete Reference

The SortedList Class

The

SortedList

 class stores a sorted list of key/value pairs. It is the generic 

equivalent of the non-generic 

SortedList

 class. 

SortedList

 implements 

IDictionary

,

IDictionary, ICollection

,

ICollection< KeyValuePair>

,

IEnumerable

, and 

IEnumerable< KeyValuePair>

. The size of a 

SortedList

TV>

 is dynamic and will automatically grow as needed. 

SortedList

 is similar to 

SortedDictionary

 but has different performance characteristics. For example, a 

SortedList

 uses less memory, but a 

SortedDictionary

 is faster when 

inserting out-of-order elements.

SortedList

 provides many constructors. Here is a sampling:

public SortedList( )

public SortedList(IDictionary 

dict

)

public SortedList(int 

capacity

)

public SortedList(IComparer 

comp

)

The first constructor creates an empty list with a default capacity. The second creates a list 

that contains the same elements as those in 

dict.

 The third lets you specify an initial capacity. 

If you know in advance that you will need a list of a certain size, then specifying that capacity 

will prevent the resizing of the list at runtime, which is a costly process. The fourth form lets 

you specify a comparison method that will be used to compare the objects contained in the list.

The capacity of a 

SortedList TV>

 list grows automatically as needed when elements 

are added to a list. When the current capacity is exceeded, the capacity is increased. The 

advantage of specifying a capacity is that you can prevent or minimize the overhead 

associated with resizing the collection. Of course, it makes sense to specify an initial 

capacity only if you have some idea of how many elements will be stored.

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

SortedList

TV>

 also defines several methods of its own. A sampling is shown in Table 24-18. Notice 

that the enumerator returned by 

GetEnumerator( )

 enumerates the key/value pairs stored 

in the list as objects of type 

KeyValuePair

.

Method

Description

public void Add(TK 

k

, TV 

v

)

Adds the key/value pair specified by 

k

 and 

v

 to 

the list. If 

k

 is already in the list, 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 list. Returns 

false other wise.

public bool ContainsValue(TV 

v

)

Returns true if 

v

 is a value in the invoking list. 

Returns false other wise.

public IEnumerator>

    GetEnumerator( )

Returns an enumerator for the invoking list.

public int IndexOfKey(TK 

k

)

Returns the index of the key specified by 

k.

 Returns 

–1 if the key is not in the list.

T

ABLE

 24-18 

Several Commonly Used Methods Defi ned by 

SortedList

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