Royal University of Phnom Penh
Visual Basic Programming Using VB.NET
TOPIC:
Procedures and Methods
Lecturer By: KEAN TAK
Group II:
1.CHEA BORA
2.BAN VATHANA
3.SEA SITHDARA
4.SAN REAKSMEY
5.CHAB BRIYA
6.NHEM SREYNEANG
7.KY PISETH
Contents
Procedure
II. General Procedure
I.
I.
II.
Function Procedure
Sub Procedure
III. Event Procedure
IV. Parameter Declaration
I.
II.
III.
IV.
ByVal keyword
ByRef keyword
Optional keyword
ParamArray keyword
Method
VI. Conclusion
V.
I.PROCEDURE
 Procedures provide a way to group a set of related
statements to perform a task.
 There are two types of Procedure:
 General Procedure
 Event Procedure
II. General Procedure
 Visual Basic includes two primary types of General
procedures: Sub Procedure and Function
Procedure.
1.Function Procedure
 A Function procedure is a group of statements
located between a Function statement and an End
Function statement.
 Function procedure are called by name from event
procedures or other procedures. Often used for
calculations, function procedures can receive
arguments and always return a value in the function
name.
Function Procedure (continue)
• You can define a Function procedure in a module,
class, or structure. It is Public by default, which
means you can call it from anywhere in your
application that has access to the module, class, or
structure in which you defined it.
• A Function procedure can take arguments, such as
constants, variables, or expressions, which are
passed to it by the calling code.
Function Procedure (continue)
 Function Syntax
The basic syntax of a function is as follow:
Function FunctonName([parameterlist]) As returntype
Function Statement
Return Value ‘FunctionName=value
End Function
Function Procedure (continue)
 FunctionName is the name of the function you’re
creating.
 As returntype is a pair of keywords that specifies the
function return type.
 Parameterlist is a list of optional arguments ( separated
by commas) to be used in the function. Each argument
should also be declared as a specific type. (By default,
Visual Basic adds the ByVal keyword to each argument,
indicating that a copy of the data is passed to the function
through this argument but that any changes to the
arguments won’t be returned to the calling routine.)
Function Procedure (continue)
 Function statement is a block of statements that
accomplishes the work of the function.
 Return is a statement which used to return a value
to the calling procedure. When a return statement
is executed, the function is exited, so if there are any
function statement after the return statement,
these won’t be executed. In order to return value to
calling procedure we can also used:
FunctionName=Value
Function Procedure (continue)
 Calling Function Procedure
 You invoke a Function procedure by including its name and
arguments either on the right side of an assignment statement
or in an expression. You must provide values for all arguments
that are not optional, and you must enclose the argument list
in parentheses. If no arguments are supplied, you can
optionally omit the parentheses.
Function Procedure (continue)
 The syntax for a call to a Function procedure is as
follows:
lvalue = functionname[(argumentlist)]
If ((functionname[(argumentlist)] / 3) <= expression) Then
-lvalue is a variable which get the value that returned from
function.
-functionname is a name of function which we want to call.
-argumentlist : is used to give the value to parameter_list in
function procedure
Function Procedure (continue)
Example: (Source Code)
Private Sub btnCalculation_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles
btnCalculation.Click
Dim n As Integer
n = Convert.ToInt32(txtInput.Text)
MessageBox.Show("Factorial(" & n & ")=" & Factorial(n), "test",)
End Sub
Function Factorial(ByVal n As Integer) As Long
Dim p As Long = 1
For i As Integer = 1 To n
p *= i
Next
Return p
'Factorial = p
End Function
Function Procedure (continue)
 Example: (Result)
When this button is clicked, event-procedure execute
and call function procedure(Factorial())to execute too.
2.Sub Procedure
 A Sub procedure is a group of statements located
between a Sub statement and an End Sub statement.
 A Sub procedure is similar to a Function procedure,
except that a Sub procedure doesn’t return a value
associated with its name. Sub procedures are
typically used to get input from the user, display or
print information, or manipulate several properties
associated with condition. Sub procedures can also
be used to process and update variables received in
an argument list during a procedure, and pass back
one or more of these values to the calling program.
Sub Procedure(continue)
 You can define a Sub procedure in modules, classes,
and structures. By default, it is Public, which means
you can call it from anywhere in your application
that has access to the module, class, or structure in
which you defined it.
 A Sub procedure can take arguments, such as
constants, variables, or expressions, which are
passed to it by the calling code.
Sub Procedure(continue)
 Sub Procedure Syntax
The basic syntax of a Sub procedure is as follow:
Sub ProcedureName([parameterlist])
procedure Statement
End Sub
Sub Procedure(continue)
 PocedureName is the name of the Sub procedure
you’re creating.
 ParameterList is a list of optional argument(
seperated by commas if there’s more than one) to be
used in the Sub procedure.Each argument should also
be declared as a specific type. (By default, Visual Basic
adds the ByVal keyword to each argument, indicating that
a copy of the data is passed to the Sub procedure through
this argument but that any changes to the arguments won’t
be returned to the calling routine.)
Sub Procedure(continue)
 Procedure statement is a block of statements that
accomplishes the work of the procedure.
Sub Procedure(continue)
 Calling Sub Procedure
 You invoke a Sub procedure explicitly with a stand-alone
calling statement. You cannot call it by using its name in an
expression. You must provide values for all arguments that are
not optional, and you must enclose the argument list in
parentheses. If no arguments are supplied, you can optionally
omit the parentheses. The use of the Call keyword is optional
but not recommended.
Sub Procedure(continue)
 The syntax for a call to a Sub procedure is as follows:
[Call] subname([argumentlist])
-Call is an optional keyword that used to call Sub
procedure to execute.
-subame is a name of Sub procedure which we want
to call.
-argumentlist : is used to give the value to
parameter_list in Sub procedure.
Sub Procedure(continue)
 Example: (Source Code)
Private Sub btnWelcome_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles btnWelcome.Click
Dim name As String
name = txtInput.Text
Greeting(name)
'Call Greeting(name)
End Sub
Sub Greeting(ByVal name As String)
MessageBox.Show("Hello " & name & " How are you?", "Greeting")
End Sub
Sub Procedure(continue)
 Example: (Result)
When this button is clicked, event-procedure execute
and call Sub procedure(Greeting()) to execute too.
III.Event Procedure
 Event Procedures are Sub procedures that execute
in response to an event raised by user action or by an
occurrence in a program.
 An event procedure is a block of code that’s
executed when an object is manipulated in a
program. For example, when the Button1 object is
clicked, the Button1_Click event procedure is
executed.
Event Procedure(continue)
 Example(source code)
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles Button1.Click
MessageBox.Show("This is an event procedure that is executed by user click
on button1")
End Sub
Event Procedure(continue)
 Example(Result)
IV.Parameter Declaration
 You declare each procedure parameter similarly to how
you declare a variable, specifying the parameter name
and data type. You can also specify the passing
mechanism, and whether the parameter is optional or a
parameter array.
 The syntax for each parameter in the parameter list is as
follows:
[Optional] [ByVal | ByRef] [ParamArray] parametername As datatype
 If the parameter is optional, you must also supply a
default value as part of its declaration. The syntax for
specifying a default value is as follows:
Optional [ByVal | ByRef] parametername As datatype = defaultvalue
1.ByVal keyword
• Parameter which is declared by keyword ByVal
cannot return the value to variable in Argument in
calling code.
ByVal keyword(continue)
 Example: (Source code)
Private Sub cmdOK_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles cmdOK.Click
Dim x As Integer
x = 10
Sum(x)
MessageBox.Show("now x=" & x)
End Sub
Sub Sum(ByVal a As Integer)
a = a + 20
End Sub
ByVal keyword(continue)
 Example: (Result)
Value of x is still equal 10
ByRef keyword
• Parameter which is declared by keyword ByRef
need to return the value to variable in Argument in
calling code.
ByRef keyword(continue)
 Example: (Source code)
Private Sub cmdOK_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles cmdOK.Click
Dim x As Integer
x = 10
Sum(x)
MessageBox.Show("now x=" & x)
End Sub
Sub Sum(ByRef a As Integer)
a = a + 20
End Sub
ByRef keyword(continue)
 Example: (Result)
X is changed value to 30
3.Optonal keyword
 Optional Keyword: Specifies that a procedure
argument can be omitted when the procedure is
called.
Optonal keyword(continue)
 Example: (Source code)
Private Sub cmdOK_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles cmdOK.Click
Dim x As Integer
x = Add10()
‘x=Add10(10)
MessageBox.Show("now x=" & x)
End Sub
Function Add10(Optional ByVal i As Integer = 1) As Integer
Dim s As Integer
s = i + 10
Return s
End Function
Optonal keyword(continue)
 Example: (Result)
4.ParamArray keyword
 ParamArray keyword:
 Specifies that a procedure parameter takes an optional array of
elements of the specified type. ParamArray can be used only
on the last parameter of a parameter list.
 ParamArray allows you to pass an arbitrary number of
arguments to the procedure. A ParamArray parameter is
always declared using ByVal.
 You can supply one or more arguments to a ParamArray
parameter by passing an array of the appropriate data type, a
comma-separated list of values, or nothing at all.
ParamArray keyword(continue)
 Example: (Source code)
Private Sub cmdOK_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles cmdOK.Click
Dim x As Integer
x = Sum(1, 2, 3, 4)
‘x = Sum(1, 2,) , x = Sum()
MessageBox.Show("now x=" & x)
End Sub
Function Sum(ByVal ParamArray a() As Integer)
Dim s As Integer
For i As Integer = 0 To UBound(a)
s = s + a(i)
Next
Return s
End Function
ParamArray keyword(continue)
 Example: (Result)
V. Method
 A Method is a procedure built into the class. They are a
series of statements that executed when called.
 The following is the example of some built-in methods:
Class
Math
Method
Description
Example
Max(x,y) Returns the larger of x and y
Max(3.4,5.6) is 5.6
Pow(x,y) Returns a specified number raised to
the specified power.
Pow(2.0,7.0) is 128.0
Sqrt(x)
Returns the square root of a specified
number.
Sqrt(9.0) is 3.0
Method(continue)
Class
Method
Description
Example
ToString()
Converts the value of this
instance to a String.
Dim a As Integer=10
a.ToString() is “10”
ToUpper()
Returns a copy of this String
converted to uppercase.
Dim s As String =“rupp”
s.ToUpper() is “RUPP”
Remove(x)
Deletes a specified number of
characters from this instance.
Dim s As String=“RUPP”
s.Remove(2) is “RU”
String
Method(continue)
Class
Method
Description
Example
BinarySearch(Array,Target)
Searches a onedimensional sorted Array
for a value, using a binary
search algorithm.
Dim instance() As Integer = {1, 2, 3,
4, 5}
Dim result As Integer
result =
Array.BinarySearch(instance, 4) is 3
Clear(Array,index,length)
Sets a range of
elements in the
Array to zero
Dim instance() As Integer = {1, 2, 3,
4, 5}
Array.Clear(instance , 1, 2) is
1,0,0,4,5
Copy(S_array,D_array,length)
Copies a range of elements
from an Array starting at
the first element and pastes
them into another Array
starting at the first element.
Dim instance() As Integer = {1, 2, 3,
4, 5}
Dim dest(4) As Integer
Array.Copy(instance, dest, 3) is
1,2,3,0,0
Array
Method(continue)
Class
Method
Description
Example
Day(DateValue)
Returns an Integer value from 1
through 31 representing the day of the
month.
Day(#12/3/1988#) is 3
WeekDay(Datevalu
e,DayOfWeek)
Returns an Integer value
containing a number
representing the day of
the week.
Dim DateValue As DateTime
Dim returnValue As Integer
Dim dayofweek As FirstDayOfWeek
DateValue = #11/12/2010#
returnValue =
DateAndTime.Weekday(DateValue,
dayofweek) is 6
Year(DateValue)
Returns an Integer value from 1
through 9999 representing the year.
Day(#12/3/1988#) is 1988
DateAndTi
me Class
VI.Conclusion
 Know about syntax of Function procedure and how
to call it.
 Know about syntax of Sub procedure how to call it.
 Know about Parameter Declaration in procedure.
 Know some methods in some classes.