VB.Net - Statements

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A statement is a complete instruction in Visual Basic programs. It may contain keywords, operators, variables, literal values, constants and expressions.

Statements could be categorized as:

  • Declaration statements - these are the statements where you name a variable, constant, or procedure, and can also specify a data type.

  • Executable statements - these are the statements, which initiate actions. These statements can call a method or function, loop or branch through blocks of code or assign values or expression to a variable or constant. In the last case, it is called an Assignment statement.

Declaration Statements

The declaration statements are used to name and define procedures, variables, properties, arrays, and constants. When you declare a programming element, you can also define its data type, access level, and scope.

The programming elements you may declare include variables, constants, enumerations, classes, structures, modules, interfaces, procedures, procedure parameters, function returns, external procedure references, operators, properties, events, and delegates.

Following are the declaration statements in VB.Net:

S.NStatements and DescriptionExample
1Dim Statement
Declares and allocates storage space for one or more variables.
Dim number As Integer
Dim quantity As Integer = 100
Dim message As String = "Hello!"
2Const Statement
Declares and defines one or more constants.
Const maximum As Long = 1000
Const naturalLogBase As Object 
= CDec(2.7182818284)
3Enum Statement
Declares an enumeration and defines the values of its members.
Enum CoffeeMugSize
    Jumbo
    ExtraLarge
    Large
    Medium
    Small
End Enum 
4Class Statement
Declares the name of a class and introduces the definition of the variables, properties, events, and procedures that the class comprises.
Class Box
Public length As Double
Public breadth As Double   
Public height As Double
End Class
5Structure Statement
Declares the name of a structure and introduces the definition of the variables, properties, events, and procedures that the structure comprises.
Structure Box
Public length As Double           
Public breadth As Double   
Public height As Double
End Structure
6Module Statement
Declares the name of a module and introduces the definition of the variables, properties, events, and procedures that the module comprises.
Public Module myModule
Sub Main()
Dim user As String = 
InputBox("What is your name?") 
MsgBox("User name is" & user)
End Sub 
End Module
7Interface Statement
Declares the name of an interface and introduces the definitions of the members that the interface comprises.
Public Interface MyInterface
    Sub doSomething()
End Interface 
8Function Statement
Declares the name, parameters, and code that define a Function procedure.
Function myFunction
(ByVal n As Integer) As Double 
    Return 5.87 * n
End Function
9Sub Statement
Declares the name, parameters, and code that define a Sub procedure.
Sub mySub(ByVal s As String)
    Return
End Sub 
10Declare Statement
Declares a reference to a procedure implemented in an external file.
Declare Function getUserName
Lib "advapi32.dll" 
Alias "GetUserNameA" 
(
  ByVal lpBuffer As String, 
  ByRef nSize As Integer) As Integer 
11Operator Statement
Declares the operator symbol, operands, and code that define an operator procedure on a class or structure.
Public Shared Operator +
(ByVal x As obj, ByVal y As obj) As obj
        Dim r As New obj
' implemention code for r = x + y
        Return r
    End Operator 
12Property Statement
Declares the name of a property, and the property procedures used to store and retrieve the value of the property.
ReadOnly Property quote() As String 
    Get 
        Return quoteString
    End Get 
End Property
13Event Statement
Declares a user-defined event.
Public Event Finished()
14Delegate Statement
Used to declare a delegate.
Delegate Function MathOperator( 
    ByVal x As Double, 
    ByVal y As Double 
) As Double 

Executable Statements

An executable statement performs an action. Statements calling a procedure, branching to another place in the code, looping through several statements, or evaluating an expression are executable statements. An assignment statement is a special case of an executable statement.

Example

The following example demonstrates a decision making statement:

Module decisions
   Sub Main()
      'local variable definition '
      Dim a As Integer = 10

      ' check the boolean condition using if statement '
      If (a < 20) Then
         ' if condition is true then print the following '
         Console.WriteLine("a is less than 20")
      End If
      Console.WriteLine("value of a is : {0}", a)
      Console.ReadLine()
   End Sub
End Module

When the above code is compiled and executed, it produces the following result:

a is less than 20;
value of a is : 10


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