' Visual Basic 2008 9.0 .NET Examples - Introduction to Functions - Procedures and Functions : 
Module Example1
    Sub Main()
        Dim value1 As Integer = 5
        Dim value2 As Integer = 10
        Dim sum As Integer
        '
        MakeSum(value1, value2, sum)
        Console.WriteLine(sum)
        '
        Console.ReadLine()
    End Sub
    Sub MakeSum(ByVal value1 As Integer, ByVal value2 As Integer, _
                ByRef sum As Integer)
        sum = value1 + value2
    End Sub
End Module
Module Example2
    Sub Main()
        Dim value1 As Integer = 5
        Dim value2 As Integer = 10
        '
        Dim sum As Integer = GetSum(value1, value2)
        Console.WriteLine(sum)
        '
        Console.ReadLine()
    End Sub
    Function GetSum(ByVal value1 As Integer, _
                    ByVal value2 As Integer) As Integer
        Return (value1 + value2)
    End Function
End Module
Module Example3
    Sub Main()
        Console.WriteLine(Test1())
        Console.WriteLine(Test2())
        '
        Console.ReadLine()
    End Sub
    Function Test1() As String
        Console.WriteLine("Test1 : code before Return statement")
        Return "Test1"
        Console.WriteLine("Test1 : code after Return statement")           ' (1)
    End Function
    Function Test2() As String
        Console.WriteLine("Test2 : code before assigning return value")
        Test2 = "Test2"
        Console.WriteLine("Test2 : code after assigning return value")
    End Function
End Module
Module Example4
    Sub Main()
        For value As Integer = -1 To 1
            Console.WriteLine("Value " & value & " : ")
            Console.WriteLine(GetInfo1(value))
            Console.WriteLine(GetInfo2(value))
            Console.WriteLine(GetInfo3(value))
            Console.WriteLine()
        Next
        '
        Console.ReadLine()
    End Sub
    Function GetInfo1(ByVal value As Integer) As String
        Select Case value
            Case Is = 0
                Return "Value is zero."
            Case Is > 0
                Return "Value is positive."
            Case Is < 0
                Return "Value is negative."
        End Select
    End Function
    Function GetInfo2(ByVal value As Integer) As String
        Dim info2 As String
        Select Case value
            Case Is = 0
                info2 = "Value is zero."
            Case Is > 0
                info2 = "Value is positive."
            Case Is < 0
                info2 = "Value is negative."
        End Select
        Return info2
    End Function
    Function GetInfo3(ByVal value As Integer) As String
        Select Case value
            Case Is = 0
                GetInfo3 = "Value is zero."
            Case Is > 0
                GetInfo3 = "Value is positive."
            Case Is < 0
                GetInfo3 = "Value is negative."
        End Select
        'Return GetInfo3                                                   ' (1)
    End Function
End Module
Module Example5
    Sub Main()
        Dim dividend As Integer = 24
        Dim divisor As Integer = 6
        Dim quotient As Single
        '
        If Not IsZero(divisor) Then quotient = GetQuotient(dividend, divisor)
        '
        Console.WriteLine(quotient)
        '
        Console.ReadLine()
    End Sub
    Function IsZero(ByVal value As Integer) As Boolean
        If value = 0 Then IsZero = True
    End Function
    Function GetQuotient(ByVal dividend As Integer, _
                         ByVal divisor As Integer) As Double
        GetQuotient = dividend / divisor
    End Function
End Module
Module Exercise1Solution
    Sub Main()
        Console.WriteLine(GetResult(5, "+"c, 4))
        Console.WriteLine(GetResult(5, "-"c, 4))
        Console.WriteLine(GetResult(5, "*"c, 4))
        '
        Console.ReadLine()
    End Sub
    Function GetResult(ByVal value1 As Integer, _
                       ByVal operatorSymbol As Char, _
                       ByVal value2 As Integer) As Integer
        Select Case operatorSymbol
            Case "+"c
                GetResult = value1 + value2
            Case "-"c
                GetResult = value1 - value2
            Case "*"c
                GetResult = value1 * value2
        End Select
    End Function
End Module
Module Exercise2Solution
    Sub Main()
        Console.WriteLine(IsLeapYear(1900))
        Console.WriteLine(IsLeapYear(1996))
        Console.WriteLine(IsLeapYear(2000))
        Console.WriteLine()
        Console.WriteLine(GetDaysFebruary(1900))
        Console.WriteLine(GetDaysFebruary(1996))
        Console.WriteLine(GetDaysFebruary(2000))
        Console.WriteLine()
        Console.WriteLine(GetDays(1900, 2))
        Console.WriteLine(GetDays(1996, 2))
        Console.WriteLine(GetDays(2000, 2))
        Console.WriteLine()
        Console.WriteLine(GetDays(1900, 3))
        Console.WriteLine(GetDays(1996, 3))
        Console.WriteLine(GetDays(2000, 3))
        '
        Console.ReadLine()
    End Sub
    Function IsLeapYear(ByVal year As Integer) As Boolean
        If year Mod 4 = 0 AndAlso year Mod 100 <> 0 OrElse _
           year Mod 400 = 0 Then IsLeapYear = True
    End Function
    Function GetDaysFebruary(ByVal year As Integer) As Integer
        GetDaysFebruary = 28
        If IsLeapYear(year) Then GetDaysFebruary = 29
    End Function
    Function GetDays(ByVal year As Integer, ByVal month As Integer) As Integer
        If month = 2 Then
            GetDays = GetDaysFebruary(year)
        Else
            Dim days As Integer() = _
                           {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
            GetDays = days(month - 1)
        End If
    End Function
End Module

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