Keywords Compared in Various Languages

Article
05/31/2012

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 Various Languages, with Code Examples.

Purpose	Visual Basic	C++	C#	F#
Declare a variable	Dim Public Friend Protected Private Shared Static1	declarators (concept, not keyword)	declarators (keywords include user-defined types and built-in types)	let Bindings Values
Declare a named constant	Const	const	const readonly	let Bindings Values
Create a new instance of a class	New	new gcnew	new	new
Create a new object	New CreateObject for COM objects	CoCreateInstance() (for COM objects)	new	new
Assign an object to an object variable	=	=	=	<-
Function/method does not return a value	Sub2	void	void	Unit Type
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)	override
Refer to the current object	Me3	this	this	Use the self-identifier as described in Methods or Members
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.	Not applicable	Not applicable
Retrieve character from a string	GetChar	(p + 10) or p[10] where p is a char or wchar_t*	str[10] where str is a string string	str.Chars(10) where str is a string Strings
Declare a compound data type (structure)	Structure Class Interface	class struct union __interface	struct class interface	Classes
Initialize an object (constructor)	Sub New()4	constructors (concept, not keyword)	Constructors, or system default type constructors Class Constructors	Constructors
Terminate an object directly	Not applicable	~ClassName	Not applicable	Not applicable
Method called by the system just before garbage collection reclaims an object5	Finalize (in Visual Basic 6.0, Class_Terminate)	Destructors (C++) (concept, not keyword)	Destructors	Finalize
Guarantee that unmanaged resources are disposed of after use	Using	Not applicable	using	Resource Management
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();	let x = 123
Take the address of a function	AddressOf (This operator returns a reference to a function in the form of a delegate instance)	delegate	delegate	Functions
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	Not applicable
Declare that an object can be modified asynchronously	Not applicable	volatile	volatile	Not applicable
Force explicit declaration of variables	Option Explicit	Not applicable (All variables must be declared prior to use)	Not applicable (All variables must be declared prior to use)	Not applicable (All variables must be declared prior to use)
Enable local type inference	Option Infer			Type inference is automatically enabled
Test for an object variable that does not refer to an object	obj Is Nothing	pobj == NULL	obj == null	Use an option type in a match expression Option Match Expressions
Value of an object variable that does not refer to an object	Nothing	nullptr	null	Null Values
Test for a database null expression	IsDBNull	Not applicable	Not applicable	Not applicable
Test whether a Variant variable has been initialized	Not applicable	Not applicable	Not applicable	Not applicable
Define a default property	Default	property: the property keyword refers to managed code	Indexers	Indexed Properties

Object-Oriented Programming

Purpose	Visual Basic	C++	C#	F#
Refer to a base class	MyBase	__super	base	base
Declare an interface	Interface	__interface interface class	interface	interface
Specify an interface to be implemented	Implements	(Just derive from the interface) class C1 : public I1	class C1 : I1 Interfaces	interface
Declare a class	Class	class Classes and Structs (Managed)	class	type
Declare a module	Module	static class	static class	module
Declare a partial definition of a class or structure	Partial	Not applicable	Partial	No direct equivalent. See Type Extensions (F#).
Specify that a class can only be inherited. An instance of the class cannot be created	MustInherit	abstract (Visual C++)6	abstract	Abstract Classes
Specify that a class cannot be inherited	NotInheritable	sealed	sealed	SealedAttribute
Declare an enumerated type	Enum	enum	enum	type
Declare a class constant	Const	const	const (Applied to a field declaration)	Values are immutable (constant) by default. See Values (F#).
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	inherit
Override a method or property	Overrides	(No language keyword required for this purpose except override for /clr compilations — see Derived Classes)	override	override
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
Declare a method that cannot be overridden	NotOverridable (Methods are NotOverridable by default.)	sealed	sealed	Use the Sealed attribute
Declare a virtual method or property, or property accessor	Overridable	virtual	virtual	abstract, as described in Methods
Hide a base class member in a derived class	Shadowing	new (new slot in vtable)	new	Hiding a virtual or abstract method is not permitted
Declare a typesafe reference to a class method	Delegate	delegate	delegate	myObj.myFunction where myObj is an object and myMethod is a method available on that object
Specify that a variable can contain an object whose events you wish to handle	WithEvents	Not applicable	(Write code - no specific keyword)	Not applicable
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)	Not applicable	event += eventHandler;	Not applicable
Evaluate an object expression once, in order to access multiple members	With... End With	Not applicable	Not applicable	Not applicable

Exception Handling

Purpose	Visual Basic	C++	C#	F#
Exception handling	Try... Catch... Finally... End Try Throw	Structured exception handling:__try, __except __finally C++ exception handling: try, catch, throw CLR exception handling: Exception Handling under /clr	try, catch, finally throw	try with finally

Exception handling

Try... Catch... Finally... End Try

Throw

Structured exception handling:__try, __except

__finally

C++ exception handling:

try, catch, throw

CLR exception handling:

Exception Handling under /clr

Decision Structures

Purpose	Visual Basic	C++	C#	F#
Decision structure (selection)	Select... Case... End Select	switch, case, default goto break	switch, case default goto break	Match Expressions
Decision structure (if ... then)	If... Then... Else... End If ElseIf	if, else	if, else	if...then...else
Loop structure (conditional)	While... End While Do...Loop	do, while continue	do while continue	while...do
Loop structure (iteration)	For... Next For Each... Next	for	for foreach	for...to for...in

Arrays

Purpose	Visual Basic	C++	C#	F#
Declare an array	Dim a() As Long	int x[5];	int[] x = new int[5];	let x = [\| 1; 2; 3; 4; 5 \|] Arrays
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};	let x = [\| 1; 2; 3; 4; 5 \|] Arrays
Reallocate array	Redim	Not applicable	Not applicable	Not applicable

Declare an array

Dim a() As Long

int x[5];

int[] x = new int[5];

let x = [| 1; 2; 3; 4; 5 |]

Arrays

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};

let x = [| 1; 2; 3; 4; 5 |]

Arrays

Reallocate array

Redim

Not applicable

Class Scope

Purpose	Visual Basic	C++	C#	F#
Visible outside the project or assembly	Public	public	public	public
Visible only within the assembly in which declared	Friend	private	internal	internal
Visible only within current or derived classes	Protected	Not applicable	Protected	Not applicable
Access is limited to the current assembly or types derived from the containing class.	Protected Friend	Type and Member Visibility	protected internal Accessibility Levels	Not applicable
Visible only within the project (for nested classes, within the enclosing class)	Private	private	private	private

Member Scope

Purpose	Visual Basic	C++	C#	F#
Accessible outside class, project, and module	Public	public	public	public
Accessible outside the class, but within the project or package	Friend	public private	internal	internal
Accessible only to current and derived classes	Protected	protected	protected	Not applicable
Only accessible within class or module	Private	private	private	private
Specify that a function or another class has access to private members of the declaring class	Not applicable	friend	Not applicable	Not applicable
Protected inside the assembly and private to other assemblies	Not applicable	protected private	Not applicable	Not applicable
Access is limited to the current assembly or types derived from the containing class	Protected Friend	Type and Member Visibility	protected internal Accessibility Levels	Not applicable

Miscellaneous Lifetime

Purpose	Visual Basic	C++	C#	F#
Preserve procedure's local variables	Static7	static	static	Not applicable
Shared by all instances of a class	Shared	static	static	static

Miscellaneous

Purpose	Visual Basic	C++	C#	F#
Comment code	' Rem	//, /* */ for multiline comments	//, /* */ for multiline comments /// for XML comments	//, (* *) for multiline comments
Case-sensitive?	No	Yes	Yes	Yes
Call Windows API	Declare <API>	Not applicable	use Platform Invoke	Use Platform Invoke. See External Functions (F#).
Declare and raise an event	Event RaiseEvent	Not applicable	event	Events
Threading primitives	SyncLock	Not applicable	lock	lock
Go to (branch)	Goto	goto	goto	Not applicable

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

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

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

7 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.

Keywords Compared in Various Languages

Object-Oriented Programming

Exception Handling

Decision Structures

Arrays

Class Scope

Member Scope

Miscellaneous Lifetime

Miscellaneous

See Also

Reference

Other Resources

Additional resources