Chapter 5 – Subroutines and Functions
5.1 What Are Subroutines and Functions?
As your applications grow, you need to break them into separate logical units.
The code associated with accomplishing each task is separated from the code theaccomplishes other tasks.
These actions are referred to as events and are one way of breaking up code into smaller, morelogical units.
Another way to break up an application is by using either functions or subroutines.
Programs are made more readable by breaking large amounts of code into smaller, moreconcise parts.
By breaking code into functions and subroutines, code can be written once and reused often.
This reduces the size of the application and debugging time.
Each time you repeat a calculation, you waste space and increase the likelihood of atypographical error and therefore cause your application to execute improperly.
Functions and subroutines operate similarly but have one key difference.
A function is used when a value is returned to the calling routine, while a subroutine is used
when a desired task is needed, but no value is returned.

1
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Invoking a Subroutine
A subroutine is used when a series of steps are required but no value is returned to the routinethat called the subroutine. Subroutines are invoked using a subroutine name:SubroutineName(ParameterList)
Invoking a subroutine can occur with parameters:
OutputMin(intValue1, intValue2)
Invoking a subroutine can also occur without parameters:
Message()2
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Invoking a Function Call
A function by definition has a return value. Therefore, a function call must be assigned to avariable of the type that the function returns:
VariableName = FunctionName(ParameterList)
The following code calls a UCase function to return an uppercase representation of a Stringthat is passed as a parameter:
strVariableName = UCase(“please uppercase this”)

3
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
5.2 Built-In Functions
Visual Basic .NET provides many built-in functions to assist your coding or applications.
By using built-in functions you save time in coding and debugging work that has already been
provided for you.

4
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
String Functions
Function Name: UCase
Function Description: Returns the String that is passed in all uppercase letters.
Common Uses: UCase can be used when the desired output is required to be in all uppercase
letters. It is also commonly used when you wish to validate data entered by a user against agiven string.
Syntax: String = UCase(String)
Examples:Function call

Return Value

UCase(“Input String”)“INPUT STRING”

UCase(“all lowercase”)“ALL LOWERCASE”

UCase(“ALL UPPERCASE”)“ALL UPPERCASE”

UCase(“UpPeP AnD lOwErCaSE”)“UPPER AND LOWERCASE”

Previous Way of Coding Validation:
If (txtVote.Text = “Bush” Or txtVote.Text = “BUSH” Or _txtVote.Text = “bush” Then ...
Better Way of Coding Validation:
If (UCase(txtVote.Text) = “BUSH”) Then ...
The Visual Basic .NET Coach5

Chapter 5 – Subroutines and Functions
Function Name: LCase
Function Description: Returns the String that is passed in all lowercase letters.
Common Uses: LCase is very similar in use to UCase.
Syntax: String = LCase(String)
Examples:Function call

Return Value

UCase(“Input String”)“input string”

UCase(“all lowercase”)“all lowercase”

UCase(“ALL UPPERCASE”)“all uppercase”

UCase(“UpPeP AnD lOwErCaSE”)“upper and lowercase”

6
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Function Name: Trim
Function Description: Returns a String with the same content, except the leading andtrailing spaces are removed.
Common Uses: Often when data is gathered, additional spaces may exist before the first
noncharacter or after the last nonblank character.
It is good practice to remove these so that data may be presented cleanly.
Syntax: String = Trim(String)
Examples:Function call

Return Value

Trim(““InputString”

InputString”)

Trim(“InputString”)“InputString”

Trim(“InputString”)“InputString”

Trim(“Input String”)“Input String”

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Function Name: Trim (continued)
The following code will initialize two Strings.
One will contain a String that has the leading and trailing spaces removed by the Trim
function.
It is displayed between two vertical bars so that it will be obvious that the spaces have been
removed.
The second String will be created in a similar manner; however, the spaces will not be
removed.
Dim strTest As String
Dim strWithBlanks As String
Dim strBorder As String
Dim strTrimmedOutput As String
Dim strUnTrimmedOutput As String|Hello|
|

Hello

|

strTest = " Hello " 'Two spaces before and after
strBorder = "|"strTrimmedOutput = strBorder & Trim(strTest) & strBorder
strUnTrimmedOutput = strBorder & strTest & strBorder
MsgBox(strTrimmedOutput)
MsgBox(strUnTrimmedOutput)
The Visual Basic .NET Coach

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Chapter 5 – Subroutines and Functions
Function Name: Space
Function Description: Returns a String containing the number of spaces indicated by theparameter.
Common Uses: Often you wish to add spaces to set the total length of a String to an exact
size.
This is often used when working with fixed-width data files.
Syntax: String = Space(Integer)
Examples:Function call

Return ValueSpace(5)“Space(10)“Space(0)“”“Hello” & Space(10) & “Goodbye”“Hello““Goodbye”

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Function Name: Len
Function Description: Returns the number of characters contained in a String
Common Uses: Len is used to determine the size of a String.
Syntax: Integer = Len(String)
Examples:Function call

Return Value

Len(“Inconceivable”)

13

Len(“Iocaine Powder”)

14

Len(“Hello, my name is Inigo Montoya. You
killed my father. Prepare to die.”)70

Len(“”)

0

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Function Name: Left
Function Description: Returns the first N characters of a String where N is an Integer
parameter indicating the number of characters to return.
If N is greater than the number of characters in the String, then the String is returned.
No extra spaces are added.
Common Uses: Often you are only concerned with the first few characters of a String. Leftis a great way to look at only the beginning of a String.
Syntax: String = Microsoft.VisualBasic.Left(String, Integer)
Examples:Function call

Return Value

Microsoft.VisualBasic.Left(“Beginning of String”, 5)“Begin”

Microsoft.VisualBasic.Left(“Beginning of String”, 2)“Be”

Microsoft.VisualBasic.Left(“Beginning of String”, 0)“”Microsoft.VisualBasic.Left(“Beginning of String”, 20)“Beginning of String”

11
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Function Name: Left (continued)
The following code shows how you might use Left to determine if a person’s full name belongs
to either a man or a woman.
Dim strPerson1 As String
Dim strPerson2 As String
Dim strPerson3 As String
Dim strPerson4 As String
strPerson1 = "Mr. Jeff Salvage"
strPerson2 = "Ms. Charlene Nolan"
strPerson3 = "Mrs. Karen Charles"
strPerson4 = "Miss Lynn Bosko"'Process Person1
If ("Mr." = Microsoft.VisualBasic.Left(strPerson1, 3)) Then
MsgBox "Person 1 is a Man"ElseIf ("Miss" = Microsoft.VisualBasic.Left(strPerson1, 4) Or _"Ms." = Microsoft.VisualBasic.Left(strPerson1, 3) Or _"Mrs." = Microsoft.VisualBasic.Left(strPerson1, 4)) Then
MsgBox "Person 1 is a Woman"Else
MsgBox "Is Person 1 an Alien?"
EndIf'Process Person2
If ("Mr." = Microsoft.VisualBasic.Left(strPerson2, 3)) Then
MsgBox "Person 2 is a Man"ElseIf ("Miss" = Microsoft.VisualBasic.Left(strPerson2, 4) Or _"Ms." = Microsoft.VisualBasic.Left(strPerson2, 3) Or _"Mrs." = Microsoft.VisualBasic.Left(strPerson2, 4)) Then
MsgBox "Person 2 is a Woman"Else
MsgBox "Is Person 2 an Alien?"
EndIf'Person3 and Person4 code could follow
The Visual Basic .NET Coach

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Chapter 5 – Subroutines and Functions
Function Name: Right
Function Description: Returns the last N characters of a String where N is an Integer
parameter indicating the number of characters to return.
If N is greater than the number of characters in the String, then the String is returned.
No extra spaces are added.
Common Uses: Often you are only concerned with the last few characters of a String.
Right is a great way to look at only the end of a String.
Syntax: String = Microsoft.VisualBasic.Right(String, Integer)
Examples:Function call

Return Value

Microsoft.VisualBasic.Right(“Ending of String”, 5)“tring”

Microsoft.VisualBasic.Right(“Ending of String”, 2)“ng”

Microsoft.VisualBasic.Right(“Ending of String”, 0)“”Microsoft.VisualBasic.Right(“Ending of String”, 20)“Ending of String”

13
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Function Name: Right (continued)
The following code shows how you might use Right to determine a person’s suffix, as in, Jr.,
Sr., or Ph.D.
Dim strPerson1 As String
Dim strPerson2 As String
Dim strPerson3 As String
strPerson1 = "Nira Herrmann, Ph.D."
strPerson2 = "John Cunningham, Sr."
strPerson3 = "Bob Bruno, Jr.“
'Process Person1
If ("Ph.D." = Microsoft.VisualBasic.Right(strPerson1, 5)) Then
MsgBox "Person 1 has a doctorate degree."
ElseIf ("Sr." = Microsoft.VisualBasic.Right(strPerson1, 3)) Then
MsgBox "Person 1 has a kid with the same name."
ElseIf ("Jr." = Microsoft.VisualBasic.Right(strPerson1, 3)) Then
MsgBox "Person 1 has a father with the same name."
EndIf'Person2 and Person3 code could follow

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Function Name: Mid
Function Description: Returns a specific number of characters of a String allowing thedeveloper to indicate where to start and how many characters to return.
The first parameter is the source String.
The second is an Integer indicating the starting position to copy from.
The third parameter is optional and indicates the number of characters to copy.
If the third parameter is left out, all characters from the starting position are returned.
Common Uses: Often you wish to extract a portion of a String to use separately from the restof the String. This is often the case when working with fixed-width data files.
Syntax: String = Mid(String, Starting Position, Optional Length)
Examples:Function call

Return Value

Mid(“This is the String”, 6, 2)“is”

Mid(“This is the String”, 9, 3)“the”

Mid(“This is the String”, 13, 4)“Stri”

Mid(“This is the String”, 8)“ the String”

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Function Name: InStr
Function Description: Returns the position of the first occurrence of a substring that issearched for in the String passed.
Common Uses: InStr can be used to tell us if a String has a certain substring contained
within it. It operates much like searching a document for a word.
Syntax: Long = InStr(String to be Searched, Search String)
Examples:Function call

Return Value

InStr(“This is a very”, “is”)

3

InStr(“ab ab ab”, “ab”)

1

InStr(“ab ab ab”, “a”)

1

InStr(“ab ab ab”, “c”)

016
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Drill 5.1
What is the output of the following code?
MsgBox UCase(“What is the output?”)
Answer: “WHAT IS THE OUTPUT?”17
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Drill 5.2
What is the output of the following code?
MsgBox Microsoft.VisualBasic.Left(“What is the output?”, 4)Answer: “What”

18
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Drill 5.3
What is the output of the following code?
MsgBox Microsoft.VisualBasic.Right(“What is the output?”, 4)Answer: “put?”

19
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Drill 5.4
What is the output of the following code?
MsgBox UCase(Microsfot.VisualBasic.Left(“What is the output?”, 4))Answer: “WHAT”

20
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Drill 5.5
What is the output of the following code?
MsgBox Microsfot.VisualBasic.Left(“What is the output?”, 4) & _Space(5) & Trim(“ ? “)Answer: “What?”21
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Conversion Functions
Function Name: Str
Function Description: Returns a String representation of the numeric value passed to it.
By default it will place a single space in front of the first numeric character.
Common Uses: Visual Basic .NET will not allow you to assign a value of one data type to avariable of another data type.
Avoid future problems by manually converting numeric values to Strings before assigningthem to either a variable of type String or a Text attribute in a control.
Syntax: String = Str(Numeric Value)
Examples:'Proper conversion
Dim strDestination As String
Dim intSource As Integer
intSource = 1
strDestination = Str(intSource)

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Function Name: Str (continued)
Here are two demonstrations of an improper conversion.
'Improper conversion
Dim strDestination As String
Dim intSource As Integer
intSource = 1
strDestination = intSource'Run-time Error
Dim strDestination As String
Dim strSource As String
strSource = "Source"
strDestination = Str(strSource)

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Function Name: Val
Function Description: Returns a numeric representation of the String value passed to it.
Val will convert a String to a numeric until it reaches a character that is not a numeric value, adecimal point, or a white-space character.
Once an unrecognizable character is read, conversion stops at that point.
Common Uses: Val is used much in the same manner as Str, except in the opposite
direction.
Syntax: Numeric Value = Val(String)
Examples:Function call

Return Value

Val(“199.11”)

199.11

Val(“

199.11“)

199.11

Val(“

1

99.1 1”)

199.11

Val(“ 199 “)

199Val(“$199.11”)0Val(“1,199.11”)

1

Val(“

0

“)

Val(“123abc”)

123

Val(“abc123”)

0

The Visual Basic .NET Coach24

Chapter 5 – Subroutines and Functions
Conversion Functions
Function Name: CDate
Function Description: Returns a Date representation of the String value passed to it.
Common Uses: CDate is used when a Date representation is needed.
Often a date can be stored in a String when it is gathered from a fixed-width or commadelimited file.
If proper operations are going to be performed on the date, then it is necessary to store it in its
native format.
Syntax: Date = CDate(String)
Examples:Dim dteToday As Date
Dim strToday As String
Dim strTomorrow As String
Dim dteTomorrow As Date
strToday = "September 30, 2001"
dteToday = CDate(strToday)'See Coach’s Tip for explanation of the DateAdd function
dteTomorrow = DateAdd(DateInterval.Day, 1, dteToday)
strTomorrow = CStr(dteTomorrow)
MsgBox(strTomorrow)
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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Drill 5.6
What is the output of the following code?
Dim sngValue1 As Single
Dim strValue2 As String
sngValue1 = 1.1
strValue2 = Str(sngValue1)
MsgBox(strValue2)
Answer: “1.1”26
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Drill 5.7
What is the output of the following code?
Dim strValue As String
strValue = Str("A")
MsgBox(strValue)
Answer: no output

27
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Mathematical Functions
Function Name: Int, Fix
Function Description: Returns the Integer portion of the numerical value passed to it.
Common Uses: Int or Fix are used when you wish to convert a numerical value to an integer
without regard for the decimal value. It performs a truncation of the number.
Syntax: Integer = Int(Numerical Value)
Integer = Fix(Numerical Value)
Examples:Function call

Return Value

Int(199.11)

199

Int(0.1)

0Int(1.5)

1

Int(0.99999)

0

Fix(199.11)

199

Fix(0.1)

028
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Drill 5.8
What is the output of the following code?
MsgBox (Str(Int(-9.9)))
Answer: -10

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Drill 5.9
What is the output of the following code?
MsgBox (Str(Fix(-9.9)))
Answer: -930
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Miscellaneous Functions
Function Name: IsNumeric
Function Description: Returns True if the value passed to it evaluates to a numeric data type,otherwise it returns False.
Common Uses: IsNumeric can be used to verify that a value can be evaluated as a number.
Instead of possibly getting either inaccurate results or a run-time error, by using IsNumeric, aproactive approach to error handling can be achieved.
Syntax: Boolean = IsNumeric(Expression)
Examples:Function call

Return Value

IsNumeric(“199.11”)

True

IsNumeric(199.11)

True

IsNumeric(“ABC”)

False

IsNumeric(“123ABC”)

False

IsNumeric(“1,999”)

True

IsNumeric(“$1,1999”)

True

IsNumeric(“50%”)

False

IsNumeric(“One”)

False
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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Function Name: IsDate
Function Description: Returns True if the value passed to it evaluates to a valid Date,otherwise it returns False.
Common Uses: IsDate can be used when you are about to convert a value to a Date
representation.
Instead of possibly getting either inaccurate results or a run-time error, by using IsDate, aproactive approach to error handling can be achieved.
Syntax: Boolean = IsDate(Expression)
Examples:Function call

Return Value

IsDate(“January 1, 2001”)

True

IsDate(“1/1/2001”)

True

IsDate(“1/1/01”)

True

IsDate(#1/1/01#)

True

IsDate(1/1/2001)

False

IsDate(“Today”)

False

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Function Name: Today
Function Description: Returns the current system date.
Common Uses: Today can be used anytime the developer wishes to access the system date.
While it is returned as a variant, it can be used as a native date format or converted to aString representation.
Syntax: Date = Today()Examples:'Code to display Yesterday’s Date in a MessageBox
Dim dteToday As Date
Dim dteYesterday As Date
Dim strYesterday As String
dteToday = Today()dteYesterday = DateAdd(DateInterval.Day, -1, dteToday)
strYesterday = CStr(dteYesterday)
MsgBox(strYesterday)

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Function Name: TimeOfDay
Function Description: Returns the current system time.
Common Uses: TimeOfDate can be used anytime the developer wishes to access thesystem time.
While it is returned as a variant, it can be used as a native date format or converted to aString representation.
You can store a Time in the DateTime data type.
Syntax: DateTime = TimeOfDay()
Examples:'Code to display the time now in a MessageBox
Dim dteExactTime As DateTime
dteExactTime = TimeOfDay()
MsgBox(dteExactTime.ToString())

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Function Name: Rnd
Function Description: Returns a pseudo random decimal number that is greater than or equal
to 0 and less than 1.
By passing Rnd an optional numeric parameter, you can further control the type of random
number you generate.
Common Uses: Random numbers are required for a great many reasons.
By combining the output of the Rnd function with some basic mathematics, random numbers
can be generated within a given range.
Syntax: Variant = Rnd()
Examples:Function call

Return Value

Int(Rnd()*3)

Generates a random number from 0 to 2

Int(Rnd()*3)+1

Generates a random number from 1 to 3

Int(Rnd()*6)+1

Generates a random number from 1 to 6

Int(Rnd()*6) +1) +(Int(Rnd()*6) +1)

Generates a random number from 2 to 12
similar to rolling a pair of dice

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Function Name: Format
Function Description: Returns a String representation of the expression passed formatted
according to instructions passed to it in the second parameter. Format may be used to improve
the appearance of numbers, dates, times, or string values.
Common Uses: Format is used anytime the user needs to beautify the output of a value.
Syntax: String = Format(Expression, String)
Second Parameter:
Standard
FormatDescription

Currency

Displays the number as a monetary value. A dollar sign precedes the number that isformatted to two decimal places. If a number requires it, a comma is placed to theleft of every three digits (except for the two for the decimal places). If the number if
negative, it is enclosed in parenthesis.

Date

There are many “Standard” date formats. “General Date” will format a date/time as
mm/dd/yyyy and hh:mm:ss if there is a time. Other formats include: “Long Date”,“Medium Date”, “Short Date”

Fixed

Displays the number with two decimal places and at least one digit to the left of thedecimal place.

Percent

Displays the number as a percentage. It multiplies the number passed by 100 (withtwo decimal places) and places a percent sign to the right.

Standard

Displays the number with two decimal places. If the number requires it, a comma isplaced to the left of every three digits. If the number is negative, a negative sign isdisplayed to the left of the number.
36
There are many “Standard” time formats: “Long Time”, “Medium Time”, “Short Time”
The Visual Basic .NET CoachTimeChapter 5 – Subroutines and Functions
Function Name: Format (continued)
Examples:Function call

Return Value

Format(123.1, “Currency”)$123.10

Format(#03/03/2001#, “Short Date”)

3/3/2001

Format(123.1, “Fixed”)

123.10Format(.1231, “Percent”)

12.31%

Format(123.1, “Standard”)

123.10Format(#10:30:01#, “Long Time”)

10:30:01 AM

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Function Name: Format (continued)
Custom format strings can be made by combining different predefined format characters.
FormatChacater

Description0A 0 in the format string is replaced by the digit from the expression thatbelongs in that space. If there is no digit for that space, the 0 is displayed.

#

When a format string specifies a #, if the expression has a digit in the position
where the # is, the digit is displayed, otherwise nothing is displayed.

Decimalpoint

Forces a decimal place to be displayed. Does not necessarily force a digit to
be displayed to the right.

Comma

Places a comma in the number. Usually used in the standard position, every
three digits to the left of the decimal place.

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Function Name: Format (continued)
Examples:Function call

Return Value

Format(123.1, “00000.00”)

00123.10

Format(0, “00000.00”)

00000.00

Format(123.1, “00000”)

00123

Format(123.1, “#######.##”)

123.1

Format(123.1, “0###.##”)

0123.1

Format(123.1, “0, ###.##”)

0,123.1

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Drill 5.10
What is the range of values produced by the following code?
MsgBox Str(Int(Rnd()*100))
Answer: Integers from 0 to 100

40
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Drill 5.11
What is the range of values produced by the following code?
MsgBox Str(Int(Rnd()*10+3))
Answer: Integers from 3 to 12

41
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Drill 5.12
What is the String produced by the following code to Format?
Format(1111.1111, “Standard”)
Answer: “1,111.11”

42
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Drill 5.13
What is the String produced by the following code to Format?
Format(452.23, “0000.000”)
Answer: “0452.230”

43
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Drill 5.14
What is the String produced by the following code to Format?
Format(#03/01/2001#, “Date”)
Answer: Date is not a standard format.

44
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
5.3 Writing Functions and Subroutines
The functions built into Visual Basic .NET are useful, but they are not all-inclusive.
There are countless functions and subroutines that developers wish were built into Visual Basic.NET, but they are not.
Because it would be impossible to predict all the routines developers require, you have theability to create your own.
The syntax for creating your own function is as follows:
Scope Function FunctionName(ParameterList) As ReturnType
BodyOfFunction()
End Function

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Coding a Function
A function is declared with a scope of either Private or Public.
Private indicates that they are usable only in the form that they are coded.
If you specify a Public scope, then the function would be visible to other forms.
Using the Function keyword makes the distinction between a function and subroutine.
The FunctionName is used to differentiate this function from any others. Naming a function
follows the same rules as naming a variable.
The ParameterList is a list of variables that will be passed to the function.
A parameter list is specified by specifying the parameter name, the keyword As, and then thedata type of the parameter.
The ReturnType is the type of value that is returned from the function. When a function is
written, it must return a value of the same data type as specified by the ReturnType. A value isreturned using the following syntax:

Return ReturnValue
The BodyOfFunction is the code that accomplishes the function’s task.

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Example: Max Function
This is an example of a function that returns the maximum of two Integers.
It compares the first parameter, intValue1, to the second parameter, intValue2.
If the first parameter is greater than the second parameter, then the first parameter is the value
returned from the function. Otherwise, the second parameter is returned.
While not explicitly tested for, when the first parameter equals the second parameter, Max
returns the second parameter.
Private Function Max(ByVal intValue1 As Integer, ByVal intValue2_
As Integer) As Integer
If (intValue1 > intValue2) Then
Return intValue1
Else
Return intValue2
End If
End Function

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Example: PayRate Function
This is an example of a function that returns the pay rate of a department. The function accepts
the department as a String parameter and returns the pay rate associated with the department.
It assumes a valid department, otherwise it returns 0.
'Declare constants for entire application, place in declarations
areas of code
Const sngSalesPayRate As Single = 25
Const sngProcessingPayRate As Single = 15
Const sngManagementPayRate As Single = 75
Const sngPhonePayRate As Single = 10
'Declare PayRate function
Private Function PayRate(ByVal strDepartment As String) As Single
Select Case strDepartment
Case "Sales"
Return sngSalesPayRate
Case "Processing"
Return sngProcessingPayRate
Case "Management"
Return sngManagementPayRate
Case "Phone"
Return sngPhonePayRate
Case Else
Return 0
End SelectEnd Function
The Visual Basic .NET Coach48

Chapter 5 – Subroutines and Functions
Coding a Subroutine
The coding of a subroutine does not vary much from the coding of a function.
The only difference is that a subroutine cannot directly return a resulting value.
The syntax for subroutine is as follows:
Scope Sub SubroutineName(ParameterList)
Body of Subroutine
End Sub

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Example: ThankYouMessage Subroutine
The ThankYouMessage subroutine outputs a message in a message box.
This particular subroutine does not contain any parameters.
A subroutine does not require parameters, they are optional.

Private Sub ThankYouMessage()
MsgBox(“Thank You Pat Croche for a Great Basketball Team!”)
End Sub

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Example: DisplayGrade Subroutine
Here is a subroutine that accepts an Integer parameter that indicates a person’s average anddisplays a MessageBox containing the letter grade associated with the person’s average.
Private Sub DisplayGrade(ByVal intStudentAverage As Integer)
Select Case intStudentAverage
Case 90 To 100
MsgBox("A")
Case 80 To 89
MsgBox("B")
Case 70 To 79
MsgBox("C")
Case 60 To 69
MsgBox("D")
Case Else
MsgBox("F")
End SelectEnd Sub
The DisplayGrade routine could be called from a button and pass a value contained in a text
box to the subroutine:
Private Sub btnDisplayGrade_Click(...
DisplayGrade(Int(txtStudentGrade.Text))
End Sub
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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Example: InitializePicture Subroutine
Subroutines can be used to change the properties of a control.
Observe the following subroutine, InitializePicture.
It accepts a picture box as the first parameter and a String containing the new picture filelocation and name as the second parameter.
The subroutine will set the Picture attribute to the new file name and set the TabStop and
BorderStyle attributes to 0.
Private Sub InitializePicture(ByVal picControl As PictureBox, _ByVal strNewPicture As String)
picControl.Image = Image.FromFile(strNewPicture)
picControl.TabStop = False
picControl.BorderStyle = 0
End Sub
The InitializePicture subroutine could be called from a button:
Private Sub btnInitialize_Click(...
InitializePicture(picPicture1,“c:\VB Coach\Chapter 5\DontTouchThis.jpg”)
End Sub

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Drill 5.15
Given the following definitions of three subroutines, show which of the following subroutine calls
are valid (assuming that Option Strict is On):
Private Sub DrillSub1(ByVal intDrillValue As Integer, _ByVal strDrillValue As String)
End Sub
Private Sub DrillSub2(ByVal strDrillValue As String, _ByVal intDrillValue As Integer)
End Sub
Private Sub DrillSub3(ByVal strStringValue As Integer, _ByVal intIntegerValue As String)
End Sub

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Drill 5.15 Continued
Dim intVal1 As Integer
Dim strVal2 As String
Dim intVal3 As Integer
Dim sngVal4 As Single
DrillSub1(intVal1, strVal2)
DrillSub1(strVal2, intVal1)
DrillSub1(intVal3, strVal2)
DrillSub2(intVal1, intVal3)
DrillSub2(sngVal4, intVal1)
DrillSub2(strVal2, intVal1)
DrillSub3(intVal1, strVal2)
DrillSub3(strVal2, intVal1)
DrillSub3(intVal1, intVal3)

Valid
Invalid
Valid
Invalid
Invalid
Valid
Valid
Invalidinvalid54
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Local Variables
Many times when you are writing a function or subroutine, data must be stored temporarily
within the routine.
The value being stored will only be required during the execution of the routine and then not
required after the routine is exited.
These local variables are declared in the same manner as the other variables you declared.
When you declare a variable within a function or subroutine, it is only accessible from within thefunction or subroutine where it is declared.
Attempts to access a local variable from outside the routine where it is defined will result in acompile error.

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Example: Final Purchase PriceThis is a subroutine that outputs the tax and final price of a purchase when passed thepurchase amount.
You may assume that the tax rate is stored in a constant called sngSalesTaxRate.
Private Sub PurchasePrice(ByVal dblPurchasePrice As Double)
Dim dblTax As Double'sngSalesTaxRate is declared as a constant earlier in the program
dblTax = dblPurchasePrice * sngSalesTaxRate
MsgBox("Purchase Price: " & dblPurchasePrice.ToString & _"Sales Tax: " & dblTax.ToString & _"Final Price: " & (dblPurchasePrice*dblTax).ToString)
End Sub56
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
5.4 Pass By Reference and Pass By Value
Visual Basic .NET allows you to declare a function or subroutine with parameters that are either
a copy (pass by value) or a reference (pass by reference) to the original value.
If you wish your application to run quickly, then passing large parameters by reference will
increase performance.
The speed comes at the risk that the original value passed can be altered unexpectedly by theroutine that is called.
Visual Basic .NET’s parameter passing defaults to pass by value for subroutines or function
calls.
Parameters like Integers, Booleans, and Decimals are relatively small and do not benefit
from passing the parameter by reference. Passing large String variables and complex
controls by value could waste time. Visual Basic .NET allows you to specify either pass byreference or pass by value.
Specifying a parameter as pass by value is accomplished by placing the keyword ByVal infront of a parameter:
Private Sub SubroutineName(ByVal Parameter1 As Type)By placing the keyword ByRef in front of a parameter, the parameter will be passed byreference. If you do not specify either, it is as if you have placed a ByVal keyword, since that isthe default.
Private Sub SubroutineName(ByRef Parameter1 As Type)The Visual Basic .NET Coach57

Chapter 5 – Subroutines and Functions
Drill 5.16
Assuming the Mystery function has been defined as follows, what is the output of the followingcode?
'Declare variables
Dim intTestValue As Integer
Dim intReturnValue As Integer'Initialize intTestValue
intTestValue = 5'Display value of intTestValue before call to Mystery
MsgBox("The value of intTestValue before the call = " & _intTestValue.ToString)'Call the Mystery Function
intReturnValue = Mystery(intTestValue)'Output the return value and intTestValue
MsgBox("The return value from the call to Mystery is " & _intReturnValue.ToString)
MsgBox("The value of intTestValue after the call = " & _intTestValue.ToString())
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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Drill 5.16 Continued
Private Function Mystery(ByRef intMaxNum As Integer) As Integer
Dim intValue As Integer
intValue = 0
intValue += intMaxNum
intMaxNum = intMaxNum - 1
intValue += intMaxNum
intMaxNum = intMaxNum - 1
intValue += intMaxNum
intMaxNum = intMaxNum - 1
Return intValue
End Function
Answer:
The value of intTestValue before the call = 5
The return value of the call to Mystery is 12
The value of intTestValue after the call = 2

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Drill 5.17
What is the output of the code in Drill 5.16 when the intMaxNum parameter is changed to passby value by changing the function declaration as follows?
Private Function Mystery(ByVal intMaxNum As Integer) As Integer
Answer: 15 5

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Drill 5.18
Assuming the DrillRoutine subroutine has been defined as follows, what is the output of thefollowing code?
Dim intTestValue1 As Integer
Dim intTestValue2 As Integer
intTestValue1 = 5
intTestValue2 = 7
DrillRoutine(intTestValue1, intTestValue2)
MsgBox(Str(intTestValue1) & " " & Str(intTestValue2))
Private Sub DrillRoutine(ByVal intParam1 As Integer, _ByRef intParam2 As Integer)
intParam1 = 10
intParam2 = 20
End Sub
Answer: 5 20

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Drill 5.19
Assuming the DrillRoutine subroutine has been defined as follows, what is the output of thefollowing code?
Dim intTestValue1 As Integer
Dim intTestValue2 As Integer
intTestValue1 = 5
intTestValue2 = 7
DrillRoutine(intTestValue1, intTestValue2)
MsgBox(Str(intTestValue1) & " " & Str(intTestValue2))
Private Sub DrillRoutine(ByRef intParam1 As Integer, _ByRef intParam2 As Integer)
intParam1 = 10
intParam2 = 20
End Sub
Answer: 10 20

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Drill 5.20
Assuming the DrillRoutine subroutine has been defined as follows, what is the output of thefollowing code?
Dim intTestValue1 As Integer
Dim intTestValue2 As Integer
intTestValue1 = 5
intTestValue2 = 7
DrillRoutine(intTestValue1, intTestValue2)
MsgBox(Str(intTestValue1) & " " & Str(intTestValue2))
Private Sub DrillRoutine(ByVal intParam1 As Integer, _ByVal intParam2 As Integer)
intParam1 = 10
intParam2 = 20
End Sub
Answer: 5 7

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Drill 5.21
Assuming the DrillRoutine subroutine has been defined as follows, what is the output of thefollowing code?
Dim intTestValue1 As Integer
Dim intTestValue2 As Integer
intTestValue1 = 5
intTestValue2 = 7
DrillRoutine(intTestValue1, intTestValue2)
MsgBox(Str(intTestValue1) & " " & Str(intTestValue2))
Private Sub DrillRoutine(intParam1 As Integer, intParam2 As Integer)
intParam1 = 10
intParam2 = 20
End Sub

Answer: 5 7

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Example: Compute Change Application Utilizing Pass By Reference
Problem Description
Develop an application that will accept as input a purchase price and an amount paid.
The application will output the change due to the person in the highest denominations of thebills and change.
Assume that you can give change in denominations of $100, $50, $20, $10, $5, $1, 25 cents,
10 cents, 5 cents, and 1 cent.

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Problem Discussion
To develop an elegant solution to this problem you need pass by reference.
The solution requires figuring out the total number of each denomination you can return.
As each number of bills or coins is determined, you must account for the corresponding amountso that you do not count the same money multiple times.
The easiest way to accomplish this is to write a single function that computes the maximum
amount of the denomination passed that can be returned.
Once the number is computed, the corresponding amount can be reduced from the remaining
money.

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Problem Solution
You are going to break your problem into sections.
The first section passes the text box controls’ values to the MakeChange subroutine that will
start the actual work of the application.
Private Sub btnMakeChange_Click(...
MakeChange(Val(txtPurchasePrice.Text), Val(txtAmountPaid.Text))
End Sub67
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Problem Solution Continued
The MakeChange subroutine will be the driver of the application. It accepts a purchase priceand the amount paid. It outputs the correct change. Instead of complicating MakeChange, youcall a support function called PrintBills.
Private Sub MakeChange(ByVal dblPurchasePrice As Double, _ByVal dblAmountPaid As Double)'Variable to store the amount of change remaining
Dim dblTotalChange As Double'Compute initial amount of change
dblTotalChange = dblAmountPaid - dblPurchasePrice'Determine how many hundred dollar bills should be returned
PrintBills(dblTotalChange, 100)
'Determine how many fifty dollar bills should be returned
PrintBills(dblTotalChange, 50)'Determine how many twenty dollar bills should be returned
PrintBills(dblTotalChange, 20)'Determine how many ten dollar bills should be returned
PrintBills(dblTotalChange, 10)'Determine how many five dollar bills should be returned
PrintBills(dblTotalChange, 5)'Determine how many dollar bills should be returned
PrintBills(dblTotalChange, 1)'Determine how many quarters should be returned
PrintBills(dblTotalChange, 0.25)'Determine how many dimes should be returned
PrintBills(dblTotalChange, 0.1)
'Determine how many nickels should be returned
PrintBills(dblTotalChange, 0.05)'Determine how many pennies should be returned
PrintBills(dblTotalChange, 0.01)
End Sub
The Visual Basic .NET Coach

68

Chapter 5 – Subroutines and Functions
Problem Solution Continued
PrintBills calculates the largest number of the current denomination by converting theresult of the division to an Integer.
Since the calculation returns an Integer value, it can be used directly as the amount of that
denomination.
Private Sub PrintBills(ByRef dblTChange As Double, ByVal
dblDenomination As Double)'Variable to store the number of bills of the current_
denomination returned
Dim intNumBills As Integer'Compute the number of bills
intNumBills = Int(dblTChange / dblDenomination)'Compute the amount of change remaining
dblTChange = dblTChange - dblDenomination * intNumBills'If there is at least one bill/coin then output the amountIf (intNumBills > 0) Then
'If the denomination is a bill (1, 5, 10, 20, 50, or 100)
If (dblDenomination >= 1) Then
'Output the bill information
lblChange.Text &= "$" & dblDenomination & " bills:" & intNumBills
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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Problem Solution Continued
PrintBills continued:'Otherwise the denomination is a coin (penny, nickel, dime, quarter)
Else'Check if it is quarter
If (dblDenomination = 0.25) Then
lblChange.Text &= "Quarters: "'Check if it is dime
ElseIf (dblDenomination = 0.1) Then
lblChange.Text &= "Dimes: "'Check if it is nickel
ElseIf (dblDenomination = 0.05) Then
lblChange.Text &= "Nickels: "'Otherwise there are pennies
Else
lblChange.Text &= "Pennies: "'Otherwise it is more than one penny
End If'Add the number of coins
lblChange.Text &= intNumBills.ToString
End If'Add a new line to the output
lblChange.Text &= vbNewLine
End IfEnd Sub
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Chapter 5 – Subroutines and Functions
5.5 Case Study
Problem Description
Modify the case study from Chapter 4 so that instead of displaying a weekly pay, you display agross pay, tax, and net pay for each employee.
Display a total gross pay, tax, and net pay for all the employees.
Also format the monetary values to appear as currency values. Compute the tax at a single rateof 28%.

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Problem Description
Since the calculations required are the same for each employee, you can write one routine that
accepts the text boxes for each employee as parameters.
You do not need to pass the employee name text box to the subroutine, since it is not used in
the calculations.

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Problem Solution
You need to remove the text boxes from Chapter 4’s solution for weekly pay and add text boxes
for gross pay, tax, and net pay.
You need one for each of the four employees.
You also need variables to store the total gross pay, total tax, and total net pay.
You can place these in the common declarations section of code along with the constants.
This code follows:'Constants to Hold Pay Rates and Tax Rate
Const intSalesPayRate = 25
Const intProcessingPayRate = 15
Const intManagementPayRate = 50
Const intPhonePayRate = 10
Const sngTaxRate = 0.28
'Temporary Variables to Store Calculations
Dim dblTmpTotalGross As Double
Dim dblTmpTotalTax As Double
Dim dblTmpTotalNet As Double
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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Problem Solution Continued
Next you must add a subroutine to compute the gross pay, tax, and net pay for a single
employee. You need to pass it the number of hours worked and the department so that you cancompute the necessary values. Additionally, you need to pass it the three text boxes that willstore the results. The code follows:
Private Sub ComputePay(ByVal txtHours As TextBox, ByVal txtDept _As TextBox, ByVal txtGross As TextBox,
ByVal txtTax As TextBox, ByVal txtNet As TextBox)
Dim dblGrossPay As Double 'Stores the calculated gross value
Dim dblTax As Double 'Stores the calculated tax
Dim dblNetPay As Double 'Stores the calculated net pay
Select Case txtDept.Text
Case "Sales"
dblGrossPay = Val(txtHours.Text) * intSalesPayRate
Case "Processing"dblGrossPay = Val(txtHours.Text) * intProcessingPayRate
Case "Management"
dblGrossPay = Val(txtHours.Text) * intManagementPayRate
Case "Phone"dblGrossPay = Val(txtHours.Text) * intPhonePayRate
Case Else
MsgBox("Error in input")dblGrossPay = 0
End Select
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Chapter 5 – Subroutines and Functions
Problem Solution Continued
ComputePay continued:
dblTax = dblGrossPay * sngTaxRate 'Compute Tax
dblNetPay = dblGrossPay - dblTax 'Compute Net Pay'Format Output
txtGross.Text = FormatCurrency(dblGrossPay)
txtTax.Text = FormatCurrency(dblTax)
txtNet.Text = FormatCurrency(dblNetPay)'Add to totals
dblTmpTotalGross += dblGrossPay
dblTmpTotalTax += dblTax
dblTmpTotalNet += dblNetPay
End Sub

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Problem Solution Continued
With the addition of the ComputePay subroutine, your btnCalculate_Click event becomeseasier.
You pass the proper parameters for each of the four employees, and then you copy the totals totheir respective text boxes.
Private Sub btnCalculate_Click(...
'First Person’s Calculations
ComputePay(txtHours1, txtDept1, txtGross1, txtTax1, txtNet1)'Second Person’s Calculations
ComputePay(txtHours2, txtDept2, txtGross2, txtTax2, txtNet2)'Third Person’s Calculations
ComputePay(txtHours3, txtDept3, txtGross3, txtTax3, txtNet3)'Fourth Person’s Calculations
ComputePay(txtHours4, txtDept4, txtGross4, txtTax4, txtNet4)'Copy the Totals to their TextBoxes
txtTotalGross.Text = FormatCurrency(dblTmpTotalGross)txtTotalTax.Text = FormatCurrency(dblTmpTotalTax)
txtTotalNet.Text = FormatCurrency(dblTmpTotalNet)
End Sub
The Visual Basic .NET Coach76

Chapter 5 – Subroutines and Functions
Problem Solution Continued
Your final application should look like this:77
The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Coach’s Corner
Stepping Over Code in Debugger
When you step through your application, you have a choice of whether you wish to step throughevery line of code or skip over code like function calls.
Observe the following simple application. It contains a button to roll a die five times.

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Stepping Over Code in Debugger Continued
The following code calls the RollDice function and returns the total value of the die roll fivetimes.
Private Sub btnRoll_Click(...
'Variable to store 5 rolls of the dice
Dim intTotal As Integer'Call the RollDice function and store the results
intTotal = RollDice()'Output the result
MsgBox(Str(intTotal))
End Sub
Private Function RollDice() As Integer
Dim intTotal As Integer
intTotal = 0
intTotal += Rnd() * 6 + 1 'First Roll
intTotal += Rnd() * 6 + 1 'Second Roll
intTotal += Rnd() * 6 + 1 'Third Roll
intTotal += Rnd() * 6 + 1 'Fourth Roll
intTotal += Rnd() * 6 + 1 'Fifth Roll
Return intTotal
End Function
The Visual Basic .NET Coach

79

Chapter 5 – Subroutines and Functions
Stepping Over Code in Debugger Continued
While you could step through this example by pressing the <F11> key or selecting Step Intofrom the Debug menu, you can skip the tracing of the function call by either hitting the <F10>
key or selecting Step Over from the Debug menu.

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Conditional Statements with Function Calls
If a function call is made within a conditional expression, all of the conditional expressions areevaluated regardless of whether or not a condition can be short-circuited. Visual Basic .NET
does this because usually if a function call is embedded in a conditional statement, the desire
was for the function to be called consistently.
The following application computes a homework average and then determines whether astudent passes.

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The Visual Basic .NET CoachChapter 5 – Subroutines and Functions
Conditional Statements with Function Calls Continued
To implement this grading scheme, the following code is used:
Private Sub butCompute_Click(...
'If the midterm grade or the Final exam grade is >= 65'ComputeHomeworkAverage will still be called
If (Val(txtMidtermGrade.Text) >= 65) Or(Val(txtFinalExamGrade.Text) >= 65)
Or (ComputeHomeworkAverage()) ThenlblFinalGrade.Text = "PASS"ElselblFinalGrade.Text = "FAIL"
End IfEnd Sub
Private Function ComputeHomeworkAverage() As Boolean'Declare variable to store the homework average
Dim sngHomeworkAverage As Single'Compute the homework average
sngHomeworkAverage = (Val(txtHomeworkGrade1.Text) + _Val(txtHomeworkGrade2.Text) + _Val(txtHomeworkGrade3.Text)) / 3'Output the homework average formatted to 2 decimal places
lblHomeworkAverage.Text = Format(sngHomeworkAverage, "0.00")'return true if the homework average is passing
If (sngHomeworkAverage >= 65) Then
Return True
Else
Return False
End If
End Function
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Chapter 5 – Subroutines and Functions
Conditional Statements with Function Calls Continued
With short circuit analysis you would expect that once the midterm grade was evaluated as
greater than or equal to 65 it would not evaluate the remaining conditions.
However, the final condition is the evaluation of the return value of a function.
Since a function is called within the condition, all the conditions are evaluated.
If the final condition was not evaluated, then the ComputeHomeworkAverage function would
not be called and the label lblHomeworkAverage would not contain the average of thehomework.

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The Visual Basic .NET Coach