VB.NET Sub-procedure and Function

Subroutine

A subroutine is a code construct.

A code construct is a pattern of coding. Examples;- For Loops, Do Whiles Loops, Sub ... End Sub, Function .... End Function

A subroutine is a self contained section of code, that;-

Has Inputs: Possible

Has Output: Never

Module mainModule

    Sub Main()

        MsgBox("The Main procedure is starting the application.")

        ' Insert call to appropriate starting place in your code.

        MsgBox("The application is terminating.")

    End Sub

End Module

Functions

A function is a self contained section of code, that;-

Has Inputs: Generally Yes

Has Output: Always

1	Function SquareOfNumber(ByVal x As Decimal) As Decimal
2	Return x * x

3	End Function

ByVal This a copy of the object passed in. You can do what you like to this and it won't change the original object passed in as the argument.

ByRef This a REFerence to the actual object. What you do to this affects the original object passed in as the argument.

A ByRef argument allows the programmer to get information out of a Subroutine, like a Function. 

Example 1 (Trivial): Increase the value of two Doubles by 2.

1	Public Sub IncreaseBothBy2(ByRef A As Double,ByRef B As Double)
2	A+=2

3	B+=2
4	End Sub

Example 2: Clear the text of any textbox.

1	Sub ClearTextbox(ByRef Tb As Textbox)
2	Tb.Text=""

3

End Sub