C# 0 The Complete Reference

ICollection

,

HashSet

 adds 

Comparer

,

shown here:

public IEqualityComparer Comparer { get; }

It obtains the comparer for the invoking hash set.

Method

Description

public T Dequeue( )

Returns the object at the front of the invoking queue. The 

object is removed in the process.

public void Enqueue(T 

v

)

Adds 

v

 to the end of the queue.

public T Peek( )

Returns the object at the front of the invoking queue, but does 

not remove it.

public T[ ] ToArray( )

Returns an array that contains copies of the elements of the 

invoking queue.

public void TrimExcess( )

Removes the excess capacity of the invoking stack.

T

ABLE

 24-20 

The Methods Defi ned by 

Queue

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Here is an example that shows 

HashSet

 in action:

// Demonstrate the HashSet class.

using System;

using System.Collections.Generic;

class HashSetDemo {

  static void Show(string msg, HashSet set) {

    Console.Write(msg);

    foreach(char ch in set)

      Console.Write(ch + " ");

    Console.WriteLine();

  }

  static void Main() {

    HashSet setA = new HashSet();

    HashSet setB = new HashSet();

    setA.Add('A');

Method

Description

public void ExceptWith(IEnumerable 

set2

)

Removes the elements in 

set2

 from the 

invoking set.

public void IntersectWith(IEnumerable 

set2

)

Removes from the invoking set those elements 

not common to both the invoking set and 

set2.

public bool

    IsProperSubsetOf(IEnumerable 

set2

)

Returns true if the invoking set is a proper 

subset of 

set2.

public bool

    IsProperSupersetOf(IEnumerable 

set2

)

Returns true if the invoking set is a proper 

superset of 

set2.

public bool IsSubsetOf(IEnumerable 

set2

)

Returns true if the invoking set is a subset 

of

set2.

public bool IsSuperSetOf(IEnumerable 

set2

)

Returns true if the invoking set is a superset 

of

set2.

public bool SetEquals(IEnumerable 

set2

)

Returns true if the invoking set is equivalent to 

set2.

 This determination is independent of the 

order of the elements.

public void

    SymmetricExceptWith(IEnumerable 

set2

)

Changes the invoking set so that it contains all 

elements from both the invoking set and 

set2,

except for those elements common to both sets. 

This is usually called the symmetric difference 

of the two sets.

public void UnionWith(IEnumerable 

set2

)

Adds the elements from 

set2

 to the invoking 

set. Duplicates are not included. Thus, it creates 

a union of the two sets.

T

ABLE

 24-21 

The Set Operations Defi ned by 

HashSet

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