Programming Microsoft Visual Basic .NET/Programming Microsoft Visual Basic .NET (Microsoft Press)(X08-78517)(2002).bin/setup/vbnet/02 modules and namespaces/modulesdemo/module1.vb

Text File | 2002-03-16 | 13.0 KB | 396 lines

Imports ModulesDemo.Animals.Mammals
Imports Acc = ModulesDemo.Computers.Accessories

Imports Microsoft.VisualBasic.Compatibility.VB6

Module MainModule

    Sub Main()
        ' Run one of the Textxxxx procedures below by uncommenting only one statement

        'TestFactorial()
        'TestBasicInheritance()
        'TestImports()
        'TestMultipleDims()
        'TestShorthands()
        'TestCollections()
        'TestBlockVariables()
        'TestDataTypes()
        'TestCollections()
        'TestFixedLenghtStrings()
        'TestInitializers()
        'TestReferenceTypes()
        'TestEnums()
        'TestArrays()
        'TestArrayInitializers()
        'TestArrayCloning()
        'TestArrayLateBinding()
        'TestCompareStructuresAndClasses()

        ' You need these statements when running inside Visual Studio, so that
        ' the Console window doesn't disappear
        Console.WriteLine("")
        Console.WriteLine(">>> press Enter to terminate the program <<<")
        Console.ReadLine()
    End Sub

    ' this procedure tests the MathFunctions.Factorial function

    Sub TestFactorial()
        Console.WriteLine("Factorial(30) = " & CStr(Factorial(30)))
    End Sub

    ' this procedure tests the VB.NET collections support the default Item member

    Sub TestCollections()
        ' The .NET version of the Collection object
        Dim col As New Microsoft.VisualBasic.Collection()
        ' Add two elements.
        col.Add("Francesco", "FirstName")
        col.Add("Balena", "LastName")
        ' The following two statements are equivalent (Item is the default member).
        Console.WriteLine(col.Item(1))            ' => Francesco
        Console.WriteLine(col(1))                 ' => Francesco
        ' The following two statements are equivalent (Item is the default member).
        Console.WriteLine(col.Item("LastName"))   ' => Balena
        Console.WriteLine(col("LastName"))        ' => Balena
    End Sub

    ' this procedure tests command math shorthands

    Sub TestShorthands()
        Dim x As Long = 9
        Dim y As Double = 6.8

        ' Increment x by one (same as x = x + 1).
        x += 1
        Console.WriteLine(x)                     ' => 10
        ' Decrement y by two (same as y = y û 2).
        y -= 2
        Console.WriteLine(y)                     ' => 4.8

        ' Double x (same as x = x * 2).
        x *= 2
        Console.WriteLine(x)                     ' => 20

        ' Divide x by ten (same as x = x \ 10).
        x \= 10
        Console.WriteLine(x)                     ' => 2

        ' Divide y by four (same as y = y / 4).
        y /= 4
        Console.WriteLine(y)                     ' => 1.2

        ' Raise y to the 3rd power (same as y = y ^ 3).
        y ^= 3
        Console.WriteLine(y)                     ' => 1.728

        Dim s As String = "abc"
        ' Append a constant to a string (same as s = s & "ABC").
        s &= "ABC"
        Console.WriteLine(2)                     ' => abcABC

        ' test performance when incrementing an object field
        ' (compile this with overflow checks removed and enabled optimization)
        Dim i As Integer
        Dim obj As New Test()
        Dim start As Date

        start = Now
        For i = 1 To 1000000000
            obj.Value += 1
        Next
        Console.WriteLine("obj.Value += 1    {0} secs.", Now.Subtract(start))

        start = Now
        For i = 1 To 1000000000
            obj.Value = obj.Value + 1
        Next
        Console.WriteLine("obj.Value = obj.Value + 1    {0} secs.", Now.Subtract(start))
    End Sub


    ' This procedure tests using a base and an inherited class

    Sub TestBasicInheritance()
        ' create an use an object
        Dim aPerson As New Person()
        aPerson.FirstName = "Joe"
        aPerson.LastName = "Doe"
        Console.WriteLine(aPerson.Title & aPerson.CompleteName)    ' => Mr. Joe Doe

        ' create and use an inherited object.
        Dim anEmployee As New Employee()
        With anEmployee
            .FirstName = "Robert"
            .LastName = "Smith"
            ' Use the new (non-inherited) members.
            .BirthDate = #2/5/1960#
            Console.WriteLine(.ReverseName)         ' => Smith, Robert
        End With

    End Sub

    ' this procedure tests the syntax for Imports statements

    Sub TestImports()
        Dim m As Mouse      ' same as Animals.Mammals.Mouse
        Dim m2 As Acc.Mouse ' same as Computers.Accessories.Mouse
        ' ...
    End Sub

    ' this procedure tests the syntax for declaratins of multiple variables

    Sub TestMultipleDims()
        ' Declare three Long variables.
        Dim x, y, z As Long

        ' Declare three variables of different type.
        Dim i As Long, k As Integer, s As String
    End Sub

    ' this procedure tests block-scoped variables

    Sub TestBlockVariables()
        Dim x, z As Integer

        ' NOTE: uncomment next line to prove that you can't have a block variable
        ' with the same name as a local variable
        'Dim y As Integer      ' Procedure variable with same name

        For x = 1 To 10
            Dim y As Integer    ' A block variable
            ' ...
        Next

        ' this block proves that you can have two block variables with same name
        ' provided that their scope isn't nested
        For z = 1 To 10
            Dim y As Integer      ' A block variable
            ' ...
        Next

        ' this block proves that inner block variables aren't reinitialized
        ' when the block is reentered.
        For z = 1 To 2
            ' ....
            For x = 1 To 2
                Dim y As Long
                y = y + 1
                Console.Write(y)                ' => 1 2 3 4
                Console.Write(" ")
            Next
        Next
        Console.WriteLine("")
    End Sub

    ' this procedure contains several tests on data types

    Sub TestDataTypes()
        Dim x As Integer

        ' Increment X if it is less than 100.
        ' (This works also when Option Strict is On.)
        x = x - CInt(x < 100)
        Console.WriteLine(x)                            ' => 1

        ' Make it clear that you're adding a Decimal constant.
        Dim d As Decimal
        d = d + 123.45@

        Dim ch As Char
        ch = "A"c        ' Note the trailing "c" character.
        ' *** The following line raises a compile error.
        ' ch = "ABC"c      ' More than one character

        ch = CChar(Mid("Francesco", 3, 1))
        Console.WriteLine(ch)                           ' => a

        ch = Chr(65)    ' This is character "A".
        Console.WriteLine(ch)                           ' => A
    End Sub

    ' this procedure tests fixed-length strings

    Sub TestFixedLenghtStrings()
        Dim s As New FixedLengthString(10)
        s.Value = "123456789012345"      ' 15 characters
        ' The characters in excess have been truncated.
        Console.WriteLine(s.Value)             ' => 1234567890
    End Sub

    ' this procedure tests initializers

    Sub TestInitializers()
        ' Two examples of variable initializers
        Dim width As Single = 1000
        Dim firstName As String = "Francesco"

        '*** Following line doesn't compile.
        ' Dim x, y, z As Long = 1

        ' you can use initializers with non-constant values
        Dim startDate As Date = Now()

        ' show that initializers can be used to re-initialize block variables
        Dim x, z As Integer
        For z = 1 To 2
            ' ....
            For x = 1 To 2
                ' Ensure that the Y variable always starts at zero.
                Dim y As Long = 0
                ' ...
            Next
        Next
    End Sub

    ' this procedure tests reference types and
    ' proves that Strings are a reference type

    Sub TestReferenceTypes()
        ' Person is a class defined in the current application.
        Dim p1 As New Person()
        p1.FirstName = "Francesco"
        ' Assign to another Person variable.
        Dim p2 As Person
        p2 = p1
        ' You can modify the original object through the new variable.
        p2.FirstName = "Joe"
        Console.WriteLine(p1.FirstName)    ' => Joe

        ' prove that strings are reference types.
        Dim s1 As String = "Francesco"
        Dim s2 As String = s1
        ' Prove that the two variables point to the same String object.
        Console.WriteLine(s2 Is s1)             ' => True
    End Sub

    ' This procedure tests Enum types

    Enum Shape
        Triangle        ' This takes a zero value.
        Square          ' 1
        Rectangle       ' 2
        Circle          ' 3
        Unknown = -999  ' (Values don't need to be sorted.)
    End Enum

    Sub TestEnums()
        ' A variable that can be assigned an Enum type.
        Dim aShape As Shape = Shape.Square

        aShape = CType(1, Shape)
    End Sub

    ' this procedure tests array operations

    Sub TestArrays()
        ' Declare the array.
        Dim arr() As Integer
        ' ...
        ' Create the array.
        ReDim arr(100)          ' Note that no As clause is used here.

        ' Declare a two-dimensional array.
        Dim arr2(,) As String
        ' Declare a three-dimensional array.
        Dim arr3(,,) As String
        ' ...
        ' Create the arrays.
        ReDim arr2(10, 10)
        ReDim arr3(10, 10, 10)

        ReDim Preserve arr2(10, 20)
        ReDim Preserve arr3(10, 10, 20)

        '*** The following statements raise an
        '    ArrayTypeMismatchException exception at runtime.
        Try

            ReDim Preserve arr2(20, 10)
            ReDim Preserve arr3(10, 20, 20)
        Catch ex As Exception
            Console.WriteLine(ex.Message)
        End Try
    End Sub

    ' this procedure tests array initializers

    Sub TestArrayInitializers()
        ' Declare and create an array of 5 integers.
        Dim arr() As Integer = {0, 1, 2, 3, 4}

        ' Declare and create a two-dimensional array of strings
        ' with two rows and four columns.
        Dim arr2(,) As String = {{"00", "01", "02", "03"}, _
                                 {"10", "11", "12", "13"}}
    End Sub

    ' this procedure tests array cloning

    Sub TestArrayCloning()
        Dim arr1() As Integer = {0, 111, 222, 333}
        Dim arr2() As Integer
        ' Create another reference to the array.
        arr2 = arr1
        ' Modify the array through the second variable.
        arr2(1) = 9999
        ' Check that the original array has been modified.
        Console.WriteLine(arr1(1))     ' => 9999

        Dim arr3() As Integer = {0, 111, 222, 333}
        ' Create a copy (clone) of the array.
        Dim arr4() As Integer = CType(arr1.Clone, Integer())
        ' Modify an element in the new array.
        arr4(1) = 9999
        ' Check that the original array hasn't been affected.
        Console.WriteLine(arr3(1))     ' => 111

        ' Copy a 2-dimensional array
        Dim arr5(,) As Integer = {{0, 1, 2, 3}, {0, 10, 20, 30}}
        Dim arr6(,) As Integer
        ' Create a copy of the 2-dimensional array.
        arr6 = CType(arr5.Clone, Integer(,))
        Console.WriteLine(arr6(1, 1))                   ' => 10

        ' you can always assign an array of reference types to an array of objects
        Dim strArr() As String = {"00", "11", "22", "33", "44"}
        Dim objArr() As Object = strArr
        Console.WriteLine(objArr(2))       ' => 22
    End Sub

    ' this procedure tests the different behavior of Structures and Classes

    Sub TestCompareStructuresAndClasses()
        ' Creation is similar, but structures don't require New.
        Dim cPers As New Person()
        Dim sPers As PersonStruct         ' New is optional.

        ' Assignment to members is identical.
        cPers.FirstName = "Joe"
        cPers.LastName = "Doe"
        sPers.FirstName = "Joe"
        cPers.LastName = "Doe"

        ' Method and property invocation is also identical.
        Console.WriteLine(cPers.CompleteName())         ' => Joe Doe
        Console.WriteLine(sPers.CompleteName())         ' => Joe Doe

        ' Assignment to a variable of the same type has different effects.

        Dim cPers2 As Person = cPers
        ' Classes are reference types, hence the new variable receives
        ' a pointer to the original object.
        cPers2.FirstName = "Ann"
        ' The original object has been affected.
        Console.WriteLine(cPers.FirstName)    ' => Ann
        '
        Dim sPers2 As PersonStruct = sPers
        ' Structure are value types, hence the new variable receives
        ' a copy of the original structure.
        sPers2.FirstName = "Ann"
        ' The original structure hasn't been affected
        Console.WriteLine(sPers.FirstName)    ' => Joe
    End Sub
End Module