C# 0 The Complete Reference

PART II

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641

The Array Class

One very useful class in 

System

 is 

Array

.

Array

 is a base class for all arrays in C#. Thus, its 

methods can be applied to arrays of any of the built-in types or to arrays of types that you 

create. 

Array

 defines the properties shown in Table 21-11. It defines the methods shown in 

Table 21-12.

Array

 implements the following interfaces: 

ICloneable

,

ICollection

,

IEnumerable

, and 

IList

.

ICollection

,

IEnumerable

, and 

IList

 are defined in the 

System.Collections

 namespace 

and are described in Chapter 24.

Several methods use a parameter of type 

IComparer

or

IComparer

. The 

IComparer

interface is in 

System.Collections

. It defines a method called 

Compare( )

, which compares 

the values of two objects. It is shown here:

int Compare(object 

v1

, object 

v2

)

It returns greater than zero if 

v1

 is greater than 

v2,

 less than zero if 

v1

 is less than 

v2,

 and 

zero if the two values are equal.

IComparer

 is in 

System.Collections.Generic

. It defines a generic form of 

Compare( )

,

which is shown here:

int Compare(T 

v1

, T 

v2

)

It works the same as its non-generic relative: returning greater than zero if 

v1

 is greater than 

v2,

 less than zero if 

v1

 is less than 

v2,

 and zero if the two values are equal. The advantage to 

IComparer

 is type safety, because the type of data being operated upon is explicitly 

specified. Thus, no casts from 

object

 are required.

The next few sections demonstrate several commonly used array operations.

public static bool Tr yParse(string 

str

,

                                        out bool 

b

)

Attempts to conver t the character in 

str

 into its 

bool

equivalent. If successful, the value is stored in 

b

 and true 

is returned. If the string is neither 

Boolean.TrueString

 nor 

Boolean.FalseString

, false is returned. (Case differences 

are ignored.) This differs from 

Parse( )

, which throws an 

exception on failure.

T

ABLE

 21-10 

Methods Defi ned by 

Boolean

(continued)

Method

Meaning

Property

Meaning

public bool IsFixedSize { get; }

A read-only proper ty that is true if the array is of fixed size and 

false if the array is dynamic. This value is true for arrays.

public bool IsReadOnly { get; }

A read-only proper ty that is true if the 

Array

 object is read-only 

and false if it is not. This value is true for arrays.

public bool IsSynchronized { get; }

A read-only proper ty that is true if the array is safe for use in a 

multithreaded environment and false if it is not. This value is 

true for arrays.

T

ABLE

 21-11 

Proper ties Defi ned by 

Array

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642

 

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public int Length { get; }

An 

int

 read-only proper ty that contains the number of elements 

in the array.

public long LongLength { get; }

A 

long

 read-only proper ty that contains the number of elements 

in the array.

public int Rank { get; }

A read-only proper ty that contains the number of dimensions in 

the array.

public object SyncRoot { get; }

A read-only proper ty that contains the object that synchronizes 

access to the array.

T

ABLE

 21-11 

Proper ties Defi ned by 

Array

(continued)

Property

Meaning

Method

Meaning

public static ReadOnlyCollection

     AsReadOnly(T[ ] 

a

)

Returns a read-only collection that wraps the array specified by 

a.

public static int Binar ySearch(Array 

a

, object 

v

)

Searches the array specified by 

a

 for the value specified by 

v.

 Returns the 

index of the first match. If 

v

 is not found, returns a negative value. The array 

must be sor ted and one-dimensional.

public static int Binar ySearch(T[ ] 

a

, T 

v

)

Searches the array specified by 

a

 for the value specified by 

v.

 Returns the 

index of the first match. If 

v

 is not found, returns a negative value. The array 

must be sor ted and one-dimensional. 

public static int

    Binar ySearch(Array 

a

, object 

v

,

                        IComparer 

comp

)

Searches the array specified by 

a

 for the value specified by 

v,

 using the 

comparison method specified by 

comp.

 Returns the index of the first match. 

If

v

 is not found, returns a negative value. The array must be sor ted and one-

dimensional.

public static int

    Binar ySearch(T[ ] 

a

, T 

v

,

                         IComparer 

comp

)

Searches the array specified by 

a

 for the value specified by 

v,

 using the 

comparison method specified by 

comp.

 Returns the index of the first match. 

If

v

 is not found, returns a negative value. The array must be sor ted and one-

dimensional.

public static int

    Binar ySearch(Array 

a

, int 

star t

,

                        int 

count

, object 

v

)

Searches a por tion of the array specified by 

a

 for the value specified by 

v.

The search begins at the index specified by 

star t

 and is restricted to 

count

elements. Returns the index of the first match. If 

v

 is not found, returns a 

negative value. The array must be sor ted and one-dimensional.

public static int

    Binar ySearch(T[ ] 

a

, int 

star t

,

                        int 

count

, T 

v

)

Searches a por tion of the array specified by 

a

 for the value specified by 

v.

The search begins at the index specified by 

star t

 and is restricted to 

count

elements. Returns the index of the first match. If 

v

 is not found, returns a 

negative value. The array must be sor ted and one-dimensional.

public static int

    Binar ySearch(Array 

a

, int 

star t

,

                        int 

count

, object 

v

,

                        IComparer 

comp

)

Searches a por tion of the array specified by 

a

 for the value specified by 

v,

using the comparison method specified by 

comp.

 The search begins at the 

index specified by 

star t

 and is restricted to 

count

 elements. Returns the 

index of the first match. If 

v

 is not found, returns a negative value. The array 

must be sor ted and one-dimensional.

public static int

    Binar ySearch(T [ ] 

a

, int 

star t

,

                        int 

count

, T 

v

,

                        IComparer 

comp

)

Searches a por tion of the array specified by 

a

 for the value specified by 

v,

using the comparison method specified by 

comp.

 The search begins at the 

index specified by 

star t

 and is restricted to 

count

 elements. Returns the 

index of the first match. If 

v

 is not found, returns a negative value. The array 

must be sor ted and one-dimensional.

T

ABLE

 21-12 

Methods Defi ned by 

Array

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