C# 0 The Complete Reference

The Generic Interfaces

System.Collections.Generic

 defines a number of generic interfaces, all of which parallel 

their corresponding non-generic counterparts. The generic interfaces are summarized in 

Table 24-10.

The ICollection Interface

The

ICollection

 interface defines those features that all generic collections have in 

common. It inherits the 

IEnumerable

 and 

IEnumerable

 interfaces. 

ICollection

 is 

the generic version of the non-generic 

ICollection

 interface. However, there are some 

differences between the two.

ICollection

 defines the following properties:

int Count { get; }

bool IsReadOnly { get; }

Count

 contains the number of items currently held in the collection. 

IsReadOnly

 is true if 

the collection is read-only. It is false if the collection is read/write.

Interface

Description

ICollection

Defines the foundational features for the generic collections.

IComparer

Defines the generic 

Compare( )

 method that per forms a 

comparison on objects stored in a collection.

IDictionar y

Defines a generic collection that consists of key/value pairs. 

IEnumerable

Defines the generic 

GetEnumerator( )

 method, which supplies the 

enumerator for a collection class.

IEnumerator

Provides members that enable the contents of a collection to be 

obtained one at a time.

IEqualityComparer

Compares two objects for equality. 

IList

Defines a generic collection that can be accessed via an indexer.

T

ABLE

 24-10 

The Generic Collection Inter faces

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ICollection

 defines the following methods. Notice it defines a few more methods 

than does its non-generic counterpart.

Method

Description

void Add(T 

obj

)

Adds 

obj

 to the invoking collection. Throws a 

NotSupportedException

 if the collection is read-only.

void Clear( )

Deletes all elements from the invoking collection and 

sets

Count

 to zero.

bool Contains(T 

obj

)

Returns true if the invoking collection contains the 

object passed in 

obj

 and false other wise.

void CopyTo(T[ ] 

target

, int 

star tIdx

)

Copies the contents of the invoking collection to 

the array specified by 

target,

 beginning at the index 

specified by 

star tIdx.

bool Remove(T 

obj

)

Removes the first occurrence of 

obj

 from the invoking 

collection. Returns true if 

obj

 was removed and false if 

it was not found in the invoking collection.

Several of these methods will throw