VB.Net's Built-in Functions

VB.Net has many built-in functions for manipulating text and carrying out mathematical operations, as well as the ability to format data in both standard and user-defined styles. We start by looking at two functions that are both frequently used and at the same time relatively easy to get to grips with - the MsgBox() function and the InputBox() function. We will then look at some of the more commonly-used string-handling and math functions, and the ways in which numerical, date and time values can be represented.


The MsgBox() function

The MsgBox() function displays a message in a pop-up message box (no surprises there!). The user is expected to respond by clicking on a button in order to be able to continue. The format of the statement used to invoke a message box is as follows:

returnVal = MsgBox (prompt, styleVal, title)

The prompt parameter is a string value (either a string literal or a string variable) that supplies the message to be displayed. The styleVal parameter is either an integer style value from 0 to 5, or a named constant that can be used instead of the corresponding integer value, that determines which command buttons will appear on the message box. The title parameter is another string literal or string variable that supplies the title for the message box.

The styles available are listed in the table below.


Message Box Styles
Style valueNamed constantButtons displayed
0vbOkOnlyOK
1vbOkCancelOK, Cancel
2vbAbortRetryIgnoreAbort, Retry, Ignore
3vbYesNoCancelYes, No, Cancel
4vbYesNoYes, No
5vbRetryCancelRetry, Cancel


The returnVal value returned by the MsgBox() function is an integer value that indicates which button the user has clicked in response to the message box being displayed. The possible return values together with the named constants that may be used in their stead, are listed in the table below.


Message Box Return Values
Return valueNamed constantButton clicked
1vbOkOK
2vbCancelCancel
3vbAbortAbort
4vbRetryRetry
5vbIgnoreIgnore
6vbYesYes
7vbNoNo


The message box can be further embellished by the inclusion of an icon that will appear beside the message. In VB.Net, there are four icons available. The icon is included either by incrementing the style value by a fixed constant value, or by the inclusion of a second named constant (see table below).


Message Box Icons
ValueNamed constantIcon
16vbCriticalCritical symbol
32vbQuestionQuestion symbol
48vbExclamationExclamation symbol
64vbInformation Information symbol


The following statements would produce exactly the same message box, and are essentially equivalent to one another:

MsgBox ("This message is for info!", 64, "Info")
MsgBox ("This message is for info!", vbOKOnly + vbInformation, "Info")



The InputBox() function

The InputBox() function displays a pop-up input box into which the user can type a message. The user is expected to enter their message, then click on a button ("Cancel" or "OK") in order to continue. The format of the statement used to invoke an input box is as follows:

returnString = InputBox (prompt, title, defaultText, xpos, ypos)

The returnString returned by the InputBox() function is the text entered by the user. The prompt parameter is a text string (either a string literal or a string variable) that prompts the user to enter some information. The title parameter is another string literal or string variable that supplies the title for the input box. The defaultText parameter can be used to enter default content in the input box (although it would probably be left blank in most cases). The xpos and ypos parameters specify the x and y coordinates for the input box on screen.


String functions


String Functions
FunctionDescription
Mid (str, pos, n)Returns n characters from the text string referred to by str, starting at character position pos.
Microsoft.VisualBasic.left (str, n)Returns the n left-most characters from the text string referred to by str.
Microsoft.VisualBasic.right (str, n)Returns the n right-most characters from the text string referred to by str.
Trim (str)Removes the white space (if any) at either end of the text string referred to by str, and returns the result.
LTrim (str)Removes the white space (if any) at the left-hand end of the text string referred to by str, and returns the result.
RTrim (str)Removes the white space (if any) at the right-hand end of the text string referred to by str, and returns the result.
InStr (n, str1, str2)Looks for an occurrence of the substring str2 within the string str1, starting at character position n. If successful, the function returns the character position at which the substring is found (or zero if the substring cannot be found).
UCase (str)Converts the string referred to by str to all upper-case characters, and returns the result.
LCase (str)Converts the string referred to by str to all lower-case characters, and returns the result.
Chr (charCode)Returns the ASCII character corresponding to the 8-bit character code charCode (note – some characters are non-printing characters, and will not be visible on screen).
Asc (character)Returns the 8-bit ASCII character code corresponding to character.



Maths functions


Maths Functions
FunctionDescription
Math.Sqrt (n) Returns the square root of a number, n.
Math.Abs (n) Returns the absolute value of a number, n.
Math.Exp (n) Returns the exponential value of a number, n – i.e. e n.
Note: e = 2.71828182
Fix (n) Returns the integer part of a floating point number, n.
Int (n) Returns the integer part of a floating point number, n, for
positive numbers, or the next smallest integer value for
negative numbers.
Math.Log (n) Returns the natural logarithm of a number, n.
Rnd () Returns a randomly generated value between 0 and 1.
Round (n,m) Rounds a number, n, up (or down) to m decimal places.



Formatting numbers

The Format() function allows you to specify precisely how numeric values are displayed. The function is used as follows:

Format (n, "styleArg")

The first argument (n) is the number to be formatted. The value selected for the second argument ("styleArg") will determine how the number is displayed. The possible values are described in the table below (note that a user-defined value for "styleArg" can also be used).


Format () Number Style Arguments
Style ArgumentDescription
"General Number"Displays n with no separator between thousands.
"Fixed"Displays n with no separator between thousands,
and rounds it up (or down) to two decimal places.
"Standard"Displays n with separators between thousands, and
rounds it up (or down) to two decimal places.
"Currency"Displays n prefixed by a "£" sign (if the locale is set
to United Kingdom) , with separators between thousands,
and rounds it up (or down) to two decimal places.
"Percent"Displays n as a percentage, rounds it up (or down) to two
decimal places, and adds a "%" symbol.



Formatting the date and time

The Format() function can also be used to specify how date and time values are displayed. The function is used as follows:

Format (Date, "styleArg")

The first argument (Date) is the date to be formatted (note that if you are using the current date, the Now function can be used as the argument. The value selected for the second argument ("styleArg") will determine how the date value is displayed. The possible values are described in the table below (note that a user-defined value for "styleArg" can also be used).


Format () Date Style Arguments
Style ArgumentDescription
"General Date"Displays the date and time in the format:
    dd/mm/yyyy hh:mm:ss
"Long Date"Displays the date in the format:
    06 October 2009
"Short Date"Displays the date in the format:
    dd/mm/yyyy
"Long Time"Displays the time in the format:
    h:mm:ss
"Short Time"Displays the time in the format:
    hh:mm