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A procedure is a group of statements that together perform a task when called. After the procedure is executed, the control returns to the statement calling the procedure. VB.Net has two types of procedures −
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Functions
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Sub procedures or Subs
Functions return a value, whereas Subs do not return a value.
Defining a Function
The Function statement is used to declare the name, parameter and the body of a function. The syntax for the Function statement is −
[Modifiers] Function FunctionName [(ParameterList)] As ReturnType [Statements] End Function
Where,
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Modifiers − specify the access level of the function; possible values are: Public, Private, Protected, Friend, Protected Friend and information regarding overloading, overriding, sharing, and shadowing.
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FunctionName − indicates the name of the function
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ParameterList − specifies the list of the parameters
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ReturnType − specifies the data type of the variable the function returns
Example
Following code snippet shows a function FindMax that takes two integer values and returns the larger of the two.
Function FindMax(ByVal num1 As Integer, ByVal num2 As Integer) As Integer '' local variable declaration */ Dim result As Integer If (num1 > num2) Then result = num1 Else result = num2 End If FindMax = result End Function
Function Returning a Value
In VB.Net, a function can return a value to the calling code in two ways −
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By using the return statement
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By assigning the value to the function name
The following example demonstrates using the FindMax function −
Module myfunctions Function FindMax(ByVal num1 As Integer, ByVal num2 As Integer) As Integer '' local variable declaration */ Dim result As Integer If (num1 > num2) Then result = num1 Else result = num2 End If FindMax = result End Function Sub Main() Dim a As Integer = 100 Dim b As Integer = 200 Dim res As Integer res = FindMax(a, b) Console.WriteLine("Max value is : {0}", res) Console.ReadLine() End Sub End Module
When the above code is compiled and executed, it produces the following result −
Max value is : 200
Recursive Function
A function can call itself. This is known as recursion. Following is an example that calculates factorial for a given number using a recursive function −
Module myfunctions Function factorial(ByVal num As Integer) As Integer '' local variable declaration */ Dim result As Integer If (num = 1) Then Return 1 Else result = factorial(num - 1) * num Return result End If End Function Sub Main() ''calling the factorial method Console.WriteLine("Factorial of 6 is : {0}", factorial(6)) Console.WriteLine("Factorial of 7 is : {0}", factorial(7)) Console.WriteLine("Factorial of 8 is : {0}", factorial(8)) Console.ReadLine() End Sub End Module
When the above code is compiled and executed, it produces the following result −
Factorial of 6 is: 720 Factorial of 7 is: 5040 Factorial of 8 is: 40320
Param Arrays
At times, while declaring a function or sub procedure, you are not sure of the number of arguments passed as a parameter.
VB.Net param arrays (or parameter arrays) come into help at these times.
The following example demonstrates this −
Module myparamfunc Function AddElements(ParamArray arr As Integer()) As Integer Dim sum As Integer = 0 Dim i As Integer = 0 For Each i In arr sum += i Next i Return sum End Function Sub Main() Dim sum As Integer sum = AddElements(512, 720, 250, 567, 889) Console.WriteLine("The sum is: {0}", sum) Console.ReadLine() End Sub End Module
When the above code is compiled and executed, it produces the following result −
The sum is: 2938
Passing Arrays as Function Arguments
You can pass an array as a function argument in VB.Net. The following example demonstrates this −
Module arrayParameter Function getAverage(ByVal arr As Integer(), ByVal size As Integer) As Double ''local variables Dim i As Integer Dim avg As Double Dim sum As Integer = 0 For i = 0 To size - 1 sum += arr(i) Next i avg = sum / size Return avg End Function Sub Main() '' an int array with 5 elements '' Dim balance As Integer() = {1000, 2, 3, 17, 50} Dim avg As Double ''pass pointer to the array as an argument avg = getAverage(balance, 5) '' output the returned value '' Console.WriteLine("Average value is: {0} ", avg) Console.ReadLine() End Sub End Module
When the above code is compiled and executed, it produces the following result −
Average value is: 214.4
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