Keywords Compared in Various Languages

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1 Keywords Compared in Various Languages Visual Studio 2010 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. Declare a variable Dim Public Friend Protected declarators (concept, not keyword) declarators (keywords include user-defined types and built-in types) let Bindings Values Private Shared Static 1 Declare a named constant Const const const readonly let Bindings Values Create a instance of a New gc Create a object New CreateObject for COM objects CoCreateInstance() (for COM objects) 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++ with a member function Func1. Not Not 1 of :29

2 Retrieve character from a string GetChar *(p + 10) or p[10] where p is a char* or str[10] where str is a string str.chars(10) where str is a wchar_t* string string Strings Declare a compound data type (structure) Structure Class struct struct Classes Interface union interface interface Initialize an object (constructor) Sub New() 4 constructors (concept, not keyword) Constructors, or system default type constructors Constructors Class Constructors Terminate an object directly Not ~ClassName Not Not Method called by the system just before garbage collection reclaims an object 5 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 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 = let x = 123 int(); 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 Declare that an object can be modified asynchronously Not volatile volatile Not 2 of :29

3 3 of :29 Force explicit declaration of variables Option Explicit Not (All variables must be declared prior to use) Not (All variables must be declared prior to use) Not (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 Not Not Test whether a Variant variable has been initialized Not Not Not Not Define a default property Default property: the property keyword refers to managed code Indexers Indexed Properties Object-Oriented Programming Refer to a base MyBase super base base Declare an interface Interface interface interface interface interface Specify an interface to be implemented Implements (Just derive from the interface) C1 : public I1 C1 : I1 Interfaces interface Declare a Class Classes and Structs (Managed) type Declare a module Module static static module Declare a partial definition of a or structure Partial Not Partial No direct equivalent. See Type Extensions (F#).

4 Specify that a can only be inherited. An instance of the cannot be created MustInherit abstract (Visual C++) 6 abstract Abstract Classes Specify that a cannot be inherited NotInheritable sealed sealed SealedAttribute Declare an enumerated type Enum enum enum type Declare a constant Const const const (Applied to a field declaration) Values are immutable (constant) by default. See Values (F#). Derive a from a base Class C1 Inherits C2 Class C1 : public Base (No language C1 : C2 inherit keyword needed for this purpose) 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 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 member in a derived Shadowing ( slot in vtable) Hiding a virtual or abstract method is not permitted Declare a typesafe reference to a 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 (Write code - no specific keyword) Not Specify the events for which an event procedure will be Handles (Event procedures can still be associated with a Not event += eventhandler; Not 4 of :29

5 5 of :29 called Evaluate an object expression once, in order to access multiple members WithEvents variable by naming pattern) With... End With Not Not Not Exception Handling Exception handling Try... Catch... Finally... End Try Throw Structured exception handling: try, except finally C++ exception handling: try, catch, finally throw try with finally try, catch, throw CLR exception handling: Exception Handling under /clr Decision Structures 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, while do while...do Do...Loop continue while continue Loop structure (iteration) For... Next for for for...to For Each... Next foreach for...in

6 Arrays Declare an array Dim a() As Long int x[5]; int[] x = 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 = int[5] {1, 2, 3, 4, 5}; let x = [ 1; 2; 3; 4; 5 ] Arrays Reallocate array Redim Not Not Not Class Scope 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 es Protected Not Protected Not Access is limited to the current assembly or types derived from the containing. Protected Friend Type and Member Visibility protected internal Not Accessibility Levels Visible only within the project (for nested es, within the enclosing ) Private private private private Member Scope Accessible outside, project, and module Public public public public Accessible outside the, but within the project or package Friend public private internal internal Accessible only to current and derived es Protected protected protected Not Only accessible within or module Private private private private 6 of :29

7 7 of :29 Specify that a function or another has access to private members of the declaring Protected inside the assembly and private to other assemblies Not friend Not Not Not protected private Not Not Access is limited to the current assembly or types derived from the containing Protected Friend Type and Member Visibility protected internal Not Accessibility Levels Miscellaneous Lifetime Preserve procedure's local variables Static7 static static Not Shared by all instances of a Shared static static static Miscellaneous 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 use Platform Invoke Use Platform Invoke. See External Functions (F#). Declare and raise an event Event RaiseEvent Not event Events Threading primitives SyncLock Not lock lock Go to (branch) Goto goto goto Not 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.

8 8 of :29 4 In Visual Basic, constructors for es 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 includes at least one pure virtual member. 7 In Visual Basic, static local variables of nonshared methods are stored per 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 Various Languages, with Code Examples Operators Compared in Various Languages Data Types Compared in Various Languages Controls and Programmable Objects Compared in Various Languages and Libraries Other Resources Language Equivalents Community Additions ; 2016 Microsoft