Keywords Compared in Different Languages

This topic lists common programming tasks that can be summarized with a language keyword. For more information about tasks that need code examples, see Programming Concepts Compared in Different Languages with Code Examples.

Purpose	Visual Basic	C++	C#	JScript	Visual FoxPro
Declare a variable	Dim Public Friend Protected Private Shared Static1	declarators (concept, not keyword)	declarators (keywords include user-defined types and built-in types)	var	[implicit declaration] PUBLIC LOCAL PRIVATE
Declare a named constant	Const	const	const readonly	const	#DEFINE
Create a new instance of a class	New	new gcnew	new	new	NEWOBJECT( ) function
Create a new object	New CreateObject() for COM objects	CoCreateInstance() (for COM objects)	new	new ActiveXObject()	CREATEOBJECT( ) function
Assign an object to an object variable	=	=	=	=	= STORE
Function/method does not return a value	Sub2	void	void	void	Void (COM servers only)
Overload a function or method (Visual Basic: overload a procedure or method)	Overloads	(No language keyword required for this purpose)	(No language keyword required for this purpose)	(No language keyword required for this purpose)	(No language keyword required for this purpose)
Refer to the current object	Me3	this	this	this	this thisform
Make a nonvirtual call to a virtual method of the current object	MyClass	MyClass::Func1(), where MyClass is a C++ class with a member function Func1.	n/a	n/a	n/a
Retrieve character from a string	GetChar Function	*(p + 10) or p[10] where p is a char* or wchar_t*	str[10] where str is a string string4	str[10], where str is a string charAt substring substr	SUBSTR( )
Declare a compound data type (structure)	Structure Class Interface	class struct union __interface	struct class interface	class, interface	n/a
Initialize an object (constructor)	Sub New()5	constructors (concept, not keyword)	Constructors, or system default type constructors Class Constructors	Constructor (concept, not keyword)6	Init event
Terminate an object directly	n/a	~ClassName	n/a	n/a	n/a
Method called by the system just before garbage collection reclaims an object7	Finalize (in Visual Basic 6.0, Class_Terminate)	Destructors (C+) (concept, not keyword)	Destructors	n/a	Destroy event
Guarantee that unmanaged resources are disposed of after use	Using	n/a	using	n/a	n/a
Initialize a variable where it is declared	Dim x As Long = 5 Dim c As New Car(FuelTypeEnum.Gas)	// initialize to a value: int x=5; //with an appropriate constructor: C c(10);	// initialize to a value: int x = 123; // or use default constructor: int x = new int();	var x = 5 var y : car = new car()	LOCAL x x = 5
Take the address of a function	AddressOf (This operator returns a reference to a function in the form of a delegate instance)	delegate	delegate	Use the name of the function without parentheses	n/a
Callback	Pass the address of one function to another that calls the invoker back. For an example, see How to: Pass Procedures to Another Procedure in Visual Basic.	CALLBACK (a standard type) callback (IDL attribute)	delegate	n/a	n/a
Declare that an object can be modified asynchronously	n/a	volatile	volatile	n/a	n/a
Force explicit declaration of variables	Option Explicit	n/a (All variables must be declared prior to use)	n/a (All variables must be declared prior to use)	fast mode (on by default)	_VFP.LanguageOptions NEW
Enable local type inference	Option Infer
Test for an object variable that does not refer to an object	obj Is Nothing	pobj == NULL	obj == null	obj == undefined obj == null	VARTYPE(obj)=="0"
Value of an object variable that does not refer to an object	Nothing	nullptr	null	null undefined	.F.
Test for a database null expression	IsDbNull	n/a	n/a	x == null	ISNULL( )
Test whether a Variant variable has been initialized	n/a	n/a	n/a	x == undefined	EMPTY( )
Define a default property	Default	property: the property keyword refers to managed code	Indexers	n/a	n/a

Object-Oriented Programming

Purpose	Visual Basic	C++	C#	JScript	Visual FoxPro
Refer to a base class	MyBase	__super	base	super	BaseClass property ParentClass property DODEFAULT() Class::member
Declare an interface	Interface	__interface interface class	interface	interface	DEFINE CLASS
Specify an interface to be implemented	Implements	(Just derive from the interface) class C1 : public I1	class C1 : I1 Interfaces	IMPLEMENTS	IMPLEMENTS NEW
Declare a class	Class	class Classes and Structs (Managed)	class	class	DEFINE CLASSMyClassAS <ParentClass>
Declare a module	Module	static class	static class	n/a	n/a
Declare a partial definition of a class or structure	Partial	n/a	Partial	n/a	n/a
Specify that a class can only be inherited. An instance of the class cannot be created	MustInherit	abstract (Visual C+)8	abstract	abstract	n/a
Specify that a class cannot be inherited	NotInheritable	sealed	sealed	final	n/a
Declare an enumerated type	Enum	enum	enum	enum	n/a
Declare a class constant	Const	const	const (Applied to a field declaration)	const	#DEFINE
Derive a class from a base class	Class C1 Inherits C2	Class C1 : public Base (No language keyword needed for this purpose)	class C1 : C2 class	Class c1 extends c2	DEFINE CLASS MyClass AS ParentClass
Override a method or property	Overrides	(No language keyword required for this purpose except override for /clr compilations — see Derived Classes)	override	(No language keyword required for this purpose)	(No language keyword required for this purpose)
Declare a method that must be implemented in a deriving class	MustOverride	Put = 0 at the end of the declaration (pure virtual method)	abstract	abstract	(No language keyword required for this purpose)
Declare a method that cannot be overridden	NotOverridable (Methods are NotOverridable by default.)	sealed	sealed	final	n/a
Declare a virtual method or property, or property accessor	Overridable	virtual	virtual	(Methods are virtual by default)	n/a
Hide a base class member in a derived class	Shadowing	new (new slot in vtable)	new	new Modifier	n/a
Declare a typesafe reference to a class method	Delegate	delegate	delegate	Use the name of the function without parentheses	n/a
Specify that a variable can contain an object whose events you wish to handle	WithEvents	n/a	(Write code - no specific keyword)	(Write code - no specific keyword)	EVENTHANDLER( ) NEW
Specify the events for which an event procedure will be called	Handles (Event procedures can still be associated with a WithEvents variable by naming pattern)	n/a	event += eventHandler;	n/a	BINDEVENTS( )
Evaluate an object expression once, in order to access multiple members	With... End With	n/a	n/a	with9	WITH ... ENDWITH

Exception Handling

Purpose	Visual Basic	C++	C#	JScript	Visual FoxPro
Structured exception handling	Try... Catch... Finally... End Try Throw	__try, __except __finally	try, catch, finally throw	try catch finally throw	TRY    [ tryCommands ] [ CATCH [ To VarName ] [ WHEN IExpression ] ]    [ catchCommands ] ] [ THROW [ eUserExpression ] ] [ EXIT ] [ FINALLY    [ finallyCommands ] ] ENDTRY
C++ exception handling	n/a	try, catch, throw	n/a	n/a	n/a

Decision Structures

Purpose	Visual Basic	C++	C#	JScript	Visual FoxPro
Decision structure (selection)	Select... Case... End Select	switch, case, default goto break	switch case default goto break	switch case break	CASE ICASE
Decision structure (if ... then)	If... Then... Else... End If ElseIf	if, else	if, else	if else	IF ... ENDIF IIF( )
Loop structure (conditional)	While... End While Do...Loop	do, while continue	do while continue	do, while break, continue	DO, WHILE (clauses)
Loop structure (iteration)	For... Next For Each... Next	for	for foreach	for (x=0;x<10;x+){...} for (prop in obj) { print (obj[prop]);}	FOR (clauses) FOR ... ENDFOR Continue NEXT FOR EACH (clauses) ,FOR ... ENDFOR, Continue, Next

Arrays

Purpose	Visual Basic	C++	C#	JScript	Visual FoxPro
Declare an array	Dim a() As Long	int x[5];	int[] x = new int[5];	var x : int[] var arr = Array()	DIMENSION DECLARE
Initialize an array	Dim a() As Long = {3, 4, 5}	int x[5]= {1,2,3,4,5};	int[] x = new int[5] {1, 2, 3, 4, 5};	var x : int[] = [1, 2, 3, 4, 5] var arr = new Array(1, 2, 3, 4, 5)]	x[1] = 1 x[2] = 2
Reallocate array	Redim	n/a	n/a	arr.length=newSize (only for JScript arrays)10	DIMENSION DECLARE

Class Scope

Purpose	Visual Basic	C++	C#	JScript	Visual FoxPro
Visible outside the project or assembly	Public	public	public	public	n/a
Visible only within the assembly in which declared	Friend	private	internal	internal	n/a
Visible only within current or derived classes	Protected	n/a	Protected	n/a	n/a
Access is limited to the current assembly or types derived from the containing class.	Protected Friend	Type and Member Visibility	protected internal Accessibility Levels	n/a	n/a
Visible only within the project (for nested classes, within the enclosing class)	Private	private	private	private	n/a

Member Scope

Purpose	Visual Basic	C++	C#	JScript	Visual FoxPro
Accessible outside class, project, and module	Public	public	public	public	(No language keyword required for this purpose)
Accessible outside the class, but within the project or package	Friend	public private:	internal	internal	n/a
Accessible only to current and derived classes	Protected	protected	protected	protected	PROTECTED
Only accessible within class or module	Private	private	private	private	HIDDEN
Specify that a function or another class has access to private members of the declaring class	n/a	friend (Not allowed in C+)	friend	n/a	n/a
Protected inside the assembly and private to other assemblies	n/a	protected private	n/a	n/a	n/a
Access is limited to the current assembly or types derived from the containing class	Protected Friend	Type and Member Visibility	protected internal Accessibility Levels	n/a	n/a

Miscellaneous Lifetime

Purpose	Visual Basic	C++	C#	JScript	Visual FoxPro
Preserve procedure's local variables	Static11	static	static	n/a	n/a
Shared by all instances of a class	Shared	static	static	static	n/a

Miscellaneous

Purpose	Visual Basic	C++	C#	JScript	Visual FoxPro
Comment code	' Rem	//, /* */ for multiline comments	//, /* */ for multiline comments /// for XML comments	//, /* */ for multiline comments	* && NOTE
Case-sensitive?	No	Yes	Yes	Yes	No
Call Windows API	Declare <API>	n/a	use Platform Invoke	n/a	DECLARE - DLL
Declare and raise an event	Event RaiseEvent	n/a	event	n/a	RAISEEVENT( ) function
Threading primitives	SyncLock	n/a	lock	n/a	n/a
Go to (branch)	Goto	goto	goto	n/a	n/a

1 In Visual Basic, the only place where Static can be used by itself to declare a variable — for example, Static x As Long — is within a procedure.

2 In Visual Basic, procedures declared with the Sub keyword cannot return values. If a procedure is to return a value, you must declare it with the Function keyword.

3 In Visual Basic, Me is not resolved at compile time, so you can use it as the return value of a property or method.

4 In JScript, the substr function is still supported, but is no longer the preferred way to access characters within a string. The most efficient way to access a character from a particular location in a string is using brackets. For example, to access the tenth character in the string str, use str[10].

5 In Visual Basic, constructors for classes derived from .NET Framework System.Object are always named New.

6 In JScript, overloading is not allowed on constructors.

7 Typically, code in such a method frees system resources that would not automatically be freed by the garbage collector.

8 In C++, an abstract class includes at least one pure virtual member.

9 In JScript, there is no leading period such as you would use in Visual Basic. This feature can easily cause confusion, because variables can be mistaken for properties, and vice versa. Also note that the with statement produces slow code.

10 In JScript, this does not reallocate the array, and does not "grow" it either. JScript arrays (declared as type Array) are always sparse and dynamic. Native arrays (declared as System.Array or as type[]) are not dynamic.

11 In Visual Basic, static local variables of nonshared class methods are stored per class instance rather than sharing a single copy, as in other languages. When Static is used to declare a variable, the value of that variable is preserved even if the variable loses and then regains scope.

See Also

Reference

Programming Concepts Compared in Different Languages with Code Examples

Operators Compared in Different Languages

Data Types Compared in Different Languages

Controls and Programmable Objects Compared in Different Languages and Libraries

Other Resources

Language Equivalents