Добавил:

Upload Опубликованный материал нарушает ваши авторские права? Сообщите нам.

Вуз:

Национальный университет Львовская политехника

Предмет:

[НЕСОРТИРОВАННОЕ]

Файл:

C# ПІДРУЧНИКИ / c# / Manning - Windows.forms.programming.with.c#.pdf

Скачиваний:

108

Добавлен:

12.02.2016

Размер:

14.98 Mб

Скачать

☆

<<< < Предыдущая 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176177 / 185177 178 179 180 181 182 183 184 185 > Следующая >>>

methods. The declaration of a delegate requires the delegate keyword employed in the following manner:

<modifiers>opt delegate <return-type> <identifier> ( <parameters>opt )

where

• <modifiers> is optional, and must be an accessibility level or the keyword new. If unspecified, a delegate is assigned the default accessibility level of the containing declarative scope. Multiple complementary modifiers may be specified.

•<return-type> is the return type for the delegate.

•<identifier> is the unique name to assign to the delegate.

•<parameters> is optional, and indicates the parameters for the delegate.

Delegate parameters are specified in the same manner as method parameters for a method within a class or structure.

A few examples of delegates are given below. Delegates are also used to create events in the Events discussion on page 644. A detailed example using a delegate appears in section 9.2.1 on page 272.

protected delegate int FindIndex(string name);

public delegate void EventHandler(object sender, EventArgs e);

public delegate Photograph ReadDelegate(StreamReader sr);

A.3 LANGUAGE ELEMENTS

This section presents the built-in types, operators, and keywords of C# in tabular form. The tables present a brief description of each item. The following aspects of the C# language are presented:

•Built-in types

•Operators

•Keywords

A.3.1 BUILT-IN TYPES

The following table summarizes the types built into C#. These types, as well as all user-defined types in C#, implicitly inherit from the object class, which also appears in this table. The table provides a short description of each type, along with each type’s default value and the class used to represent the type in the .NET Framework. Within C# source files written for the framework, the type and the .NET class are interchangeable.

C# built-in types

Type	Description	Default value	.NET class

bool	A boolean value	false	System.Boolean
byte	An unsigned 8-bit integer	(byte)0	System.Byte

654	APPENDIX A C# PRIMER

C# built-in types (continued)

Type	Description	Default value	.NET class
char	A 16-bit Unicode character	'\0'	System.Char
decimal	A 128-bit decimal value	0.0m	System.Decimal
double	A 64-bit floating point value	0.0d	System.Double
float	A 32-bit floating point value	0.0f	System.Single
int	A 32-bit integer	0	System.Int32
long	A 64-bit integer	0L	System.Int64
object	Any object. The ultimate base class of	null	System.Object
	any type.
sbyte	An 8-bit integer	(sbyte)0	System.SByte
short	A 16-bit integer	0	System.Int16
string	A reference type of a collection of char	null	System.String
	types
uint	An unsigned 32-bit integer	0u	System.UInt32
ulong	An unsigned 64-bit integer	(ulong)0	System.UInt64
ushort	An unsigned 32-bit integer	(ushort)0	System.UInt16

A.3.2 OPERATORS

Many of the operators in C# are taken from C++ and have identical meanings. The following table summarizes the operators available as they relate to the built-in types. Most of these operators may be overridden for user-defined types. Keyword operators such as true, new, and is are not shown in this table. These are summarized in the table of keywords given in the next section.

C# operators

Category	Operators	Examples

Arithmetic	+ - * / %	int num = -12;
		int age = days / 365;
		int onesPlace = number % 10;
Logical (boolean and bitwise)	& \| ^ ! ~ && \|\|	bool isTrue = ! false;
		int choices = gates & openSet;
String concatenation	+	string hi = "Hello " + "World!";
Increment, decrement	++ --	index ++;
Shift	<< >>	long kilobyte = 1 << 10;
Relational	== != > < <= >=	bool isDigit = (x >= 0) && (x < 10);

Assignment	= += -= *= /= %= &=	int byFives += 5;
	\|= ^= <<= >>=
Member access	.	return myString.ToLower();

LANGUAGE ELEMENTS

655

C# operators (continued)

Category	Operators	Examples
Indexing	[]	Photograph first = _album[0];
Cast	()	short num = (short)7;
		Photograph photo = (Photograph) obj;
Conditional	?:	int size
		= (list == null) ? 0 : list.Count;
Delegates	+ - += -=	photo.Display += new
		DisplayHandler(photo_Display);
Indirection and Address (in	* -> {} &	int num = 11;
unsafe code only)		int* pnum = &num;

A.3.3 KEYWORDS

This section presents a complete list of all keywords used by C#, along with a description and example of each keyword. These keywords are reserved words that have special meanings to the C# compiler, and should not normally be used as identifiers in your programs. To use a reserved keyword as an identifier, prefix the string with an atsign ‘@’ character. For example, while class is a reserved keyword, @class is a valid identifier.

Some of these keywords are discussed in detail in section A.2 beginning on page 639. Many of these keywords also appear elsewhere in the book. Sometimes a detailed discussion is provided, and sometimes the keyword just occurs as part of the presented code. The “See also” column in the following table provides a reference to these sections where appropriate:

C# keywords

Keyword	Description	Example	See also

abstract	Indicates that a class cannot	// Define an abstract class	sealed;
	be instantiated and is intended	public abstract class Person	Menu class in
	as a base for other classes.	{	.NET Table 3.1,
	as a base for other classes.	// Define abstract members	.NET Table 3.1,
		// Define abstract members	page 72
		public abstract string Address;	page 72
		public abstract Point GetHomeCoord();
		. . .
		}
	Within an abstract class,		sealed
	indicates that a property or
	method has no
	implementation and must be
	overridden in a derived class.
as	Converts an expression to a	object obj = lstPhotos.SelectedItem;	is;
	given type. On an error, returns	Photograph photo = obj as Photograph;	example in
	the value null.		section 9.3.4,
			page 300

656	APPENDIX A C# PRIMER

C# keywords	(continued)

Keyword	Description	Example	See also

base	Represents the base class	See example for override keyword.	example in
	from within a derived class.		section 5.3.3,
			page 148
bool	Denotes a boolean type, with	bool result = photo.IsValidImage();	true;
	possible values true and	bool isExample = true;	false;
	false.		discussion in
			section 3.4.1,
			page 89
break	Terminates the enclosing loop	foreach (Photograph p in _album)	case;
	or conditional construct.	{	examples in
	Execution resumes after the	if (p == myPhoto)	section 6.7.1,
	Execution resumes after the	break;	section 6.7.1,
	terminated construct.	break;	page 190 and
	terminated construct.	}	page 190 and
			section 18.1.2,
			page 607
byte	Denotes an unsigned 8-bit	char c = 'y';
	integer value, with values 0 to	byte b = Convert.ToByte(c);
	255.
case	Identifies a possible	See example for switch keyword.	default;
	expression within a switch		switch;
	statement.		discussion in
			section 6.7.1,
			page 190 and
			section 9.2.1,
			page 272
catch	Identifies a type of exception	See example for try keyword.	try; finally
	to handle in a try-catch		throw; section
	statement.		2.3.2 on page
			58
char	Denotes a Unicode 16-bit	char response = ReadResponse();
	character value.	char yes = 'y', no = 'n';
checked	Performs integer overflow	try	unchecked;
	checking on the given	{
	statement. If an overflow	y = checked(a/b + c);
	statement. If an overflow	}
	occurs, an exception is raised.	}
	occurs, an exception is raised.	catch (System.OverflowException e)
	By default, all integer	{
	expressions are checked.	. . .
		}
class	Defines a new data	See examples for const and override	struct;
	abstraction, or data type, along	keywords.	chapter 5 on
	with a set of members that		Reusable
	interact with this type. Classes		Libraries,
	are represented as reference		section 5.1,
	types. A class can inherit from		page 127
	at most one other class and
	from multiple interfaces.

LANGUAGE ELEMENTS

657

C# keywords	(continued)

Keyword	Description	Example	See also

const	Indicates that a field or variable	public class BookReference	readonly;
	cannot be modified. The value	{	example in
	for a constant must be	// Must be assigned here	section 6.6.1,
	for a constant must be	protected int timeout = 30;	section 6.6.1,
	assigned as part of the	protected int timeout = 30;	page 182
	assigned as part of the	protected const string defaultURL	page 182
	declaration.	= "www.manning.com/eebrown";
		// Assigned here or in constructor
		public readonly string bookURL;
		BookReference(string name, string url)
		{
		if (url == null)
		bookURL = defaultURL;
		else
		bookURL = url;
		. . .
		}
		}
continue	Passes control to the next	for (int x = 0;	example in
	iteration of the enclosing loop.	x < Contractors.Count;	section 15.3.2,
		x++)	page 498,
		{	page 498,
		{	listing 15.1
		if (Contractors[x].IsSalaried)	listing 15.1
		continue;
		// Determine hourly pay
		}
decimal	Denotes a decimal number	decimal circumference;
	with up to roughly 28	decimal radius = 7m;
	significant digits. Stored as a	decimal pi = 3.1415;
	significant digits. Stored as a	circumference = 2m * pi * radius;
	128-bit data value. Use the	circumference = 2m * pi * radius;
	128-bit data value. Use the
	suffix m or M to denote a
	numeric value as a decimal
	type.
delegate	Defines a reference type that	// Define the ReadDelegate delegate	discussion in
	encapsulates a method with a	public delegate Photograph	section 1.3.1,
	specific signature.	ReadDelegate(StreamReader sr);	page 20;
	specific signature.		page 20;
			example in
			section 9.2.1,
			page 272
default	In a switch block, identifies the	See example for switch keyword.	case;
	statement to execute if none		switch;
	of the given constant		discussion in
	expressions match the given		section 6.7.1,
	expression.		page 190 and
			section 9.2.1,
			page 272
do	Executes a statement or block	do	while;
	one or more times until a	{	example in
	specified while expression	name = reader.ReadLine();	section 6.7.1,
	specified while expression	if (name != null)	section 6.7.1,
	evaluates to false.	if (name != null)	page 190
	evaluates to false.	// Make use of the name	page 190
		} while (name != null);

658	APPENDIX A C# PRIMER

C# keywords	(continued)

Keyword	Description	Example	See also

double	Denotes a 64-bit floating point	double circumference;	float;
	value. By default, all non-	double radius = 7d;
	integral numbers are treated as	double pi = 3.1415;
	values of this type. Use the d	circumference = 2d * pi * radius;
	values of this type. Use the d
	or D suffix to denote a numeric
	value as a double type.
else	In an if statement, the	See example for if keyword.	if; examples
	statement to execute if the		throughout text
	expression returns false.
enum	Denotes an enumeration, or	enum WeekDays= { Sun, Mon, Tue, Wed,	example in
	enumerated type, consisting of	Thu, Fri, Say };	section 7.2.2,
	a defined set of constants each		page 199
	assigned a value from a given
	integral type.
event	Defines a handler abstraction	class Photograph	delegate;
	in which to define a set of	{	section 1.3.1,
	methods that should be	public event ReadDelegate LoadPhoto;	page 20 and
	methods that should be	. . .	page 20 and
	invoked when a specific	. . .	section 3.3,
	invoked when a specific	}	section 3.3,
	incident, or event, occurs.		page 85
	Methods are added or
	removed to an event with the
	+= and -= operators.
explicit	Declares that a type	public static explicit	implicit;
	conversion must be invoked	operator Photograph(string s)
	with a cast. Omitting the cast	{
	with a cast. Omitting the cast	// code to convert from string
	results in a compile-time error.	// code to convert from string
	results in a compile-time error.	}
extern	Modifies a class member	class Photograph
	declaration to indicate that the	{
	member is implemented	public extern void Draw(Graphics g);
	member is implemented	. . .
	outside the current class file.	. . .
	outside the current class file.	}
false	As an operator in user-defined	public static bool	true;
	types, defines the meaning of	operator false(MyType x)
	“false” for instances of that	{
	“false” for instances of that	// Return whether MyType is "false"
	type.	// Return whether MyType is "false"
	type.	}
	As a literal, the boolean value	bool isChapter = false;	true;
	of false.		discussion in
			section 3.4.2,
			page 93
finally	Indicates a block of code that	See example for try keyword.	catch;
	executes regardless of		try;
	whether an exception occurs		throw;
	in the preceding try block.		example in
			section 6.6.1,
			page 182

LANGUAGE ELEMENTS

659

C# keywords	(continued)

Keyword	Description	Example	See also

fixed	In unsafe code, prevents	// In unsafe code, pin current photo	unsafe
	relocation of a variable by the	fixed (Photograph photo = CurrentPhoto)
	garbage collector.	{
	garbage collector.	// Perform unsafe operations
		// Perform unsafe operations
		}
		// CurrentPhoto no longer pinned
float	Denotes a 32-bit floating point	float circumference;	double
	value. Use the f or F suffix to	float radius = 7f;
	denote a numeric value as a	float pi = 3.1415f;
	denote a numeric value as a	circumference = 2f * pi * radius;
	float type.	circumference = 2f * pi * radius;
	float type.
for	Executes a statement or block	public bool FindPhoto(string name,	foreach;
	repeatedly as long as a given	out int index)	example in
	expression evaluates to true.	{	section 10.2.2,
	expression evaluates to true.	for (int x = 0; x < this.Count; x++)	section 10.2.2,
		for (int x = 0; x < this.Count; x++)	page 328
		{	page 328
		if (this[x].Name == name)
		{
		index = x; // assign out param
		return true;
		}
		}
		return false;
		}
foreach	Executes a statement or block	foreach (Photograph p in CurrentAlbum)	for; in;
	using every element in an array	{	example in
	or collection, if any.	// Do something with each Photograph	section 3.4.2,
	or collection, if any.	}	section 3.4.2,
		}	page 93 and
			page 93 and
			section 5.1.1,
			page 128
goto	Transfers program control	do
	directly to a labeled statement.	{
	Note: The use of this keyword	// Do something
	Note: The use of this keyword	if (unable to continue)
	is generally discouraged.	goto CleanUp;
		// Do something else
		} while ( some expression );
		CleanUp:
		f.Close();
	In a switch statement,	switch (version)
	transfers control to a given	{
	case label or to the default	case 67:
	case label or to the default	photo = Photograph.ReadVer67(s);
	label.	photo = Photograph.ReadVer67(s);
	label.	goto default;
		case 77:
		// Version 77 specific tasks
		goto case 67;
		default:
		Photograph.ReadGlobalData(s);
		Break;
		}

660	APPENDIX A C# PRIMER

C# keywords	(continued)

Keyword	Description	Example	See also

if	A control statement in which a	if (_album.Count > 0)	else; examples
	statement is executed only if a	DisplayPhotos(_album);	throughout
	given expression evaluates to	else	book
	given expression evaluates to	statusBar.Text = "Album is empty";	book
	true.	statusBar.Text = "Album is empty";
	true.
implicit	Declares that a type	public static implicit	explicit
	conversion should be invoked	operator Photograph(Bitmap img)
	automatically by the compiler	{
	automatically by the compiler	// code to convert from Bitmap
	as required.	// code to convert from Bitmap
	as required.	}
in	In a foreach block, separates	See example for foreach keyword.	foreach
	the identifier from the
	expression.
int	Denotes a 32-bit integer value.	int apprxCircum	long;
	Integer values are treated as	int radius = 7;	short
	int by default. Note that there	int pi = 31415;
	is no implicit conversion from	apprxCircum = 2 * pi * radius / 10000);
	is no implicit conversion from
	floating point values to int.
interface	Defines a new data	interface IBookDisplay	class;
	abstraction, or data type, in	{	struct;
	which all members are	// Declaration of interface members	section 5.1 on
	which all members are	}	section 5.1 on
	implicitly abstract. A class or	}	page 127
	implicitly abstract. A class or		page 127
	structure can inherit from
	multiple interfaces.
internal	Access modifier for types and	See example for public keyword.	public;
	type members that indicates		protected;
	the identifier is only accessible		private;
	by objects within the same		see section
	assembly.		16.4.1, page
			543
is	Identifies whether a given	object obj = lstPhotos.SelectedItem;	as;
	expression can be converted,	if (obj is Photograph)	discussion in
	or cast, to a given type.	{	section 3.4.1,
	or cast, to a given type.	Photograph photo = (Photograph) obj;	section 3.4.1,
		Photograph photo = (Photograph) obj;	page 89
		. . .	page 89
		}
lock	Marks a statement block as a	public void SortPhotos(bool ascending)
	critical section, ensuring that	{
	only one thread can execute	lock (this)
	only one thread can execute	{
	the statement block at a time.	{
	the statement block at a time.	. . .
		}
		}
long	Denotes a 64-bit integer value.	long apprxCircum	int;
	Use the L suffix to denote an	long radius = (long)7;	short
	integer value as a long type.	long pi = (long) 314159265;
	integer value as a long type.	apprxCircum
	The l suffix may also be used,	apprxCircum
	The l suffix may also be used,	= 2L * pi * radius / 100000000L);
	but is easily confused with the
	number 1 and is not
	recommended.

LANGUAGE ELEMENTS

661

C# keywords	(continued)

Keyword	Description	Example	See also

namespace	Declares a scope for organizing	namespace MyPhotoAlbum	example in
	code and naming types and	{	section 5.2.1,
	members. If no namespace is	class PhotoAlbum : CollectionBase	page 134;
	members. If no namespace is	{	page 134;
	defined, an object is part of the	{	step in section
	defined, an object is part of the	. . .	step in section
	unnamed, or global,	}	9.1.1, page 265
	namespace.	}
new	As an operator, creates an	int index = new int();	discussion on
	object and invokes its	string s;	page section
	constructor. Value types are	Photograph photo = new Photograph(s);	1.1.3, page 9
	constructor. Value types are		1.1.3, page 9
	created in place, while	s = new string();
	reference types are created on
	the heap.
	As a modifier, explicitly hides a	public MainForm : Form	override;
	member inherited from a	{	discussion in
	derived class. This is typically	. . .	section 5.4.2,
	derived class. This is typically	protected new void OnLoad(EventArgs e)	section 5.4.2,
	used to give a new meaning or	protected new void OnLoad(EventArgs e)	page 154
	used to give a new meaning or	{	page 154
	purpose to an identifier.	. . .
		}
		}
null	Literal that represents an	Photograph photo = _album.CurrentPhoto;	examples
	uninitialized state, often	if (photo != null)	throughout text
	referred to as a null reference.	{
	referred to as a null reference.	// Do something with photograph
	This is the default value for all	// Do something with photograph
	This is the default value for all	}
	reference types.
object	The base class of all types in	object o1 = 7;	.NET Table 5.3
	C#. Any value of any type can	object o2 = new string("hear me roar!");	on page 155
	be assigned to variables of	object o3 = _album.CurrentPhoto;
	be assigned to variables of
	type object.
operator	Declares the behavior of an	public static Complex	explicit;
	operator when used with a	operator –(Complex x)	implicit
	specific type, such as a class	{
	specific type, such as a class	return new Complex(-x.Real, -x.Imgn);
	or structure. Three kinds of	return new Complex(-x.Real, -x.Imgn);
	or structure. Three kinds of	}
	operators are supported: unary	public static Complex
	operators, binary operators,	public static Complex
	and conversion operators.	operator +(Complex x, Complex y)
	and conversion operators.	{
		{
		return new Complex(x.Real + y.Real,
		x.Imgn + y.Imgn);
		}
out	Indicates that any changes	See example for for keyword.	ref;
	made to a method parameter		params
	should be reflected in the
	variable when control returns
	to the caller. A variable used as
	an out method parameter may
	be uninitialized.

662	APPENDIX A C# PRIMER

C# keywords	(continued)

Keyword	Description	Example	See also

override	Explicitly replaces a member	public class CollectionBase	new;
	inherited from a derived class.	{	discussion in
	This is typically used to provide	. . .	section 5.4.2,
	This is typically used to provide	public virtual void Clear()	section 5.4.2,
	a more appropriate	public virtual void Clear()	page 154
	a more appropriate	{	page 154
	implementation of an inherited	// Base implementation of Clear
	member in the current type.	}
		}
		public class PhotoAlbum : CollectionBase
		{
		. . .
		public override void Clear()
		{
		// Override implementation of Clear
		base.Clear();
		}
		public static void Main()
		{
		CollectionBase c = new PhotoAlbum();
		// invokes PhotoAlbum.Clear
		c.Clear();
		}
		}
params	Indicates that a method will	public void AddRange	out;
	receive a set of parameters.	(params Photograph[] photos)	ref
	This can occur only once and at	{
	the end of the list of	foreach (Photograph p in photos)
	the end of the list of	{
	parameters.	_album.Add(p);
		}
		}
private	Access modifier for types and	public class PhotoAlbum : CollectionBase	internal;
	type members that indicates	{	section 1.2.2,
	the object or member is	// only available within this class	page 16 and
	the object or member is	private int _defaultPhotoIndex;	page 16 and
	accessible only to the type in	private int _defaultPhotoIndex;	section 9.1.1,
	accessible only to the type in		section 9.1.1,
	which it is defined.	// Only available in this assembly	page 265
		internal bool IsDisplayed
		{
		. . .
		}
		// available to any derived class
		protected void TurnPage()
		{
		. . .
		}
		// available to any type
		public Photogram CurrentPhoto
		{
		. . .
		}
		}

LANGUAGE ELEMENTS

663

C# keywords	(continued)

Keyword	Description	Example	See also

protected	Access modifier for types and		section 1.2.2,
	type members that indicates		page 16 and
	the object or member is only		section 9.1.1,
	accessible by the containing		page 265
	type or by types derived from
	the containing type.
public	Access modifier for types and		section 1.2.2,
	type members that indicates		page 16 and
	the object or member is		section 9.1.1,
	accessible by any type.		page 265
readonly	Indicates that a field cannot be	See example for const keyword.	const
	assigned except in the
	declaration of the field or the
	constructor of the containing
	type.
ref	Indicates that any changes	// Locate photo after given index	out;
	made to a method parameter	public bool FindPhotoAfter	params;
	should be reflected in the	(string name, ref int index)	section 18.1.2,
	should be reflected in the	{	section 18.1.2,
	variable when control returns	{	page 607
	variable when control returns	. . .	page 607
	to the caller. Unlike the out	}
	keyword, a variable used as a
	ref method parameter must
	be initialized.
return	Terminates execution of the	See example for for keyword.	examples
	containing method and passes		throughout text
	control and the result of the
	method back to the caller.
sbyte	Denotes a signed 8-bit integer	sbyte sb = 'y';	byte
	value from –128 to 127. An	sbyte sb = (sbyte)5; e
	explicit cast is required to
	convert an integer value to a
	sbyte type.
sealed	Indicates that a class cannot	public sealed class	sealed;
	be inherited. A sealed class	SecurePerson : Person	Application
	cannot also be abstract.	{	class on
	cannot also be abstract.	. . .	class on
	Note that struct types are	. . .	page 12
	Note that struct types are	}	page 12
	implicitly sealed.
short	Denotes a 16-bit integer value	short apprxCircum	int;
	from –32,768 to 32,768. An	short radius = (short)7;	long
	explicit cast is required to	short pi = (short) 314;
	explicit cast is required to	apprxCircum
	convert an integer value to a	apprxCircum
	convert an integer value to a	= (short)(2 * pi * radius / 100);
	short type.
sizeof	Determines the size in bytes of	int size1 = sizeof(long);
	a value type.	int size2 = sizeof(Rectangle);
		int size3 = sizeof(Complex);

664	APPENDIX A C# PRIMER

C# keywords	(continued)

Keyword	Description	Example	See also

stackalloc	In unsafe code, allocates a	public unsafe void QuickSort()	unsafe
	block of memory on the stack	{
	and returns a pointer to this	Photograph* photos
	and returns a pointer to this	= stackalloc Photograph[Count];
	block. This memory is not	= stackalloc Photograph[Count];
	block. This memory is not
	subject to garbage collection	// Sort album contents
	and is valid only within the	// using local memory
	method in which it is defined.	}
	method in which it is defined.
static	Declares a member that is	private string _defaultDir	example in
	associated with the type itself	= @"C:\My Documents\Albums";	section 5.4.1,
	rather than with each instance	public static string DefaultAlbumDir	page 151
	of that type.	public static string DefaultAlbumDir
	of that type.	{
		get { return _defaultDir; }
		set { _defaultDir = value; }
		}
string	Object representing a set of	string s = null;	discussion in
	Unicode characters. While	string defaultAlbum = "myAlbum";	section 5.4.2,
	string is a reference type, the	string _defaultDir	page 154
	string is a reference type, the	= @"C:\My Documents\Albums";	page 154
	equality operators == and !=	= @"C:\My Documents\Albums";
	equality operators == and !=
	are defined to compare values
	rather than references.
struct	Defines a new data	struct Complex	class;
	abstraction, or data type, along	{	discussion in
	with a set of members that	double real;	section 1.1.3,
	with a set of members that	double imaginary;	section 1.1.3,
	interact with this type.	double imaginary;	page 9
	interact with this type.	}	page 9
	Structures are represented as
	value types, and are implicitly
	sealed.
switch	Executes one of a given set of	switch (version)	case;
	statements based on the	{	default;
	constant value of a given	case 67:	discussion in
	constant value of a given	photo = Photograph.ReadVer67(s);	discussion in
	expression. If a match for the	photo = Photograph.ReadVer67(s);	section 6.7.1,
	expression. If a match for the	break;	section 6.7.1,
	current value is not found, then	. . .	page 190 and
	a default statement can	default:	section 9.2.1,
	optionally be executed.	default:	page 272
	optionally be executed.	throw ApplicationException(	page 272
		throw ApplicationException(
		"Unrecognized album version");
		}
this	Represents the current	See example for for keyword.	example in
	instance for which a method is		section 1.1.2,
	called. Static member		page 8
	functions cannot employ the
	this keyword.
throw	Raises a new exception, or re-	See example for switch keyword.	try;
	raises a caught exception.		catch;
			section 2.3.2,
			page 58)

LANGUAGE ELEMENTS

665

C# keywords	(continued)

Keyword	Description	Example	See also

true	As in operator in user-defined	public static bool	false
	types, defines the meaning of	operator true(MyType x)
	“true” for instances of that	{
	“true” for instances of that	// Return whether MyType is "true"
	type.	// Return whether MyType is "true"
	type.	}
	As a literal, the boolean value	bool isAppendix = true;	false;
	of true.		discussion in
			section 3.4.2,
			page 93
try	Begins a block in which	// Open a file	catch
	exceptions may be handled,	FileStream fs = new FileStream(...);	finally
	depending on the attached	try	throw
	catch clauses.	try	section 2.3.2,
	catch clauses.	{	section 2.3.2,
		// Do something with open file	page 58
		}
		catch (IOException ex)
		{
		// Handle caught exception
		}
		finally
		{
		fs.Close(); // ensure file closure
		}
typeof	Obtains the System.Type	Type t = typeof(Photograph);	code in section
	object for a given type. Use the		10.5.3, page
	Object.GetType method to		348
	obtain the type instance for an
	expression.
uint	Denotes an unsigned 32-bit	uint apprxCircum	ulong;
	integer value. Use the u or U	uint radius = 7u, pi = 314159;	ushor
	suffix to denote an integer	apprxCircum
	suffix to denote an integer	= 2u * pi * radius / 100000u;
	value as a uint type.	= 2u * pi * radius / 100000u;
	value as a uint type.
ulong	Denotes an unsigned 64-bit	ulong apprxCircum	ulong;
	integer value. When using the	ulong radius = 7L;	ushort
	L suffix to denote a long	ulong pi = 31415926535
	L suffix to denote a long	apprxCircum
	integer or the U suffix to	= 2 * pi * radius / 10000000000L);
	denote an unsigned integer,
	the value is considered ulong if
	it is beyond the range of the
	long or uint type,
	respectively.
unchecked	Suppresses integer overflow	long bigPrime = 9876543211;	checked
	checking on the given	long notSoBigNum
	statement. If an overflow	= unchecked(bigPrime * bigPrime);
	statement. If an overflow
	occurs, the result is truncated.
	By default, all integer
	expressions are checked.

666	APPENDIX A C# PRIMER

<<< < Предыдущая 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176177 / 185177 178 179 180 181 182 183 184 185 > Следующая >>>

Соседние файлы в папке c#

#
12.02.20163.74 Mб67Apress - Expert Service-Oriented Architecture in C# 2005, Second Edition.pdf
#
12.02.20161.66 Mб47Apress - Expert Service-Oriented Architecture in C#_ Using the Web Services Enhancements 2.0.pdf
#
12.02.20167.64 Mб106Hungry Minds - ASP.NET Bible VB.NET & C#.pdf
#
12.02.20164.21 Mб224Hungry Minds - C# Bible.pdf
#
12.02.20169.71 Mб101Hungry Minds - Visual C# Blueprint.pdf
#
12.02.201614.98 Mб108Manning - Windows.forms.programming.with.c#.pdf
#
12.02.201616.87 Mб173MS Press - Msdn Training Programming Net Framework With C#.pdf
#
12.02.20162.56 Mб126MS Press - Oop With MS Vb Net And C# Step By Step (2002).pdf
#
12.02.201614.7 Mб443Premier Press - C# Professional Projects.pdf
#
12.02.20167.98 Mб115Sybex - VC#.NET.Programming.pdf
#
12.02.2016899.33 Кб91TestKing - Developing.WinBased.App.With.VC#.NET.pdf