Programming Microsoft Visual Basic .NET/Programming Microsoft Visual Basic .NET (Microsoft Press)(X08-78517)(2002).bin/06 interfaces and delegates/interfacesdemo/module1.vb

Text File | 2002-03-16 | 7.5 KB | 219 lines

Module MainModule

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

        'TestInterface()
        'TestInterfaceOnStructure()
        'TestIComparable()
        'TestIComparer()
        'TestIComparer2()
        'TestICloneable()
        'TestICloneable2()
        'TestICloneable3()
        'TestICloneable4()
        'TestIEnumerable()
        'TestGetEnumerator()

        ' 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

    ' the following procedure accesses an interface of a class

    Sub TestInterface()
        ' An instance of the class
        Dim addin As New MyAddin()
        ' Cast to an interface variable.
        Dim iplug As IPluggableAddin = addin
        ' Now you can access all the methods and properties in the interface.
        iplug.State = True

        ' Cast to the interface type and invoke a method in one operation.
        DirectCast(addin, IPluggableAddin).OnConnection("MyHost")

        ' Create a hidden, temporary interface variable.
        With DirectCast(addin, IPluggableAddin)
            .OnConnection("MyHost")
            .State = True
        End With

        Dim addin2 As New AnotherAddin()
        ' Prove that the AnotherAddin inherited class exposes the IPluggableAddin interface.
        DirectCast(addin2, IPluggableAddin).State = True

        ' The Dispose method in the derived class invokes the MyAddin.Dispose method
        addin2.Dispose()
    End Sub

    ' Test interfaces on structures

    Sub TestInterfaceOnStructure()
        ' this code proves that value types are boxed when an interface method is called
        Dim struc As MyStruct

        ' Get the object reference from the structure
        Dim o1 As Object = CType(struc, IGetObjectRef).GetObjectRef
        ' Do the same once again
        Dim o2 As Object = CType(struc, IGetObjectRef).GetObjectRef

        ' prove that the object has been boxed twice to different areas in the heap
        Console.WriteLine(o1 Is o2)                    ' => False
    End Sub

    ' This procedure demonstrates the IComparable interface

    Sub TestIComparable()
        Dim Persons() As Person = {New Person("John", "Smith"), _
            New Person("Robert", "Doe"), New Person("Joe", "Doe")}
        Array.Sort(Persons)

        ' Print all the elements in sorted order.
        Dim p As Person
        For Each p In Persons
            Console.WriteLine(p.ReverseName)
        Next
    End Sub

    ' this procedure demonstrates how you can use the IComparer interface

    Sub TestIComparer()
        Dim Persons() As Person2 = {New Person2("John", "Smith"), _
            New Person2("Robert", "Doe"), New Person2("Joe", "Doe")}

        ' Sort the array on name.
        Array.Sort(Persons, New Person2.ComparerByName())
        ' another way to reach the same result using a shared method
        Array.Sort(Persons, Person2.CompareByName)

        ' Print all the elements in sorted order.
        Console.WriteLine("Elements sorted on name:")
        Dim p As Person2
        For Each p In Persons
            Console.WriteLine(p.CompleteName)
        Next

        ' Sort the array on reversed name.
        Array.Sort(Persons, New Person2.ComparerByReverseName())
        ' another way to reach the same result using a shared method
        Array.Sort(Persons, Person2.CompareByReverseName)

        Console.WriteLine("Elements sorted on reverse name:")
        For Each p In Persons
            Console.WriteLine(p.ReverseName)
        Next
    End Sub

    ' this procedure tests sorts in case sensitive way

    Sub TestIComparer2()
        Dim arr() As String = {"aaa", "AAA", "Abc", "ABC", "abc", "aBC", "aaα", "αbc"}
        Dim s As String

        Array.Sort(arr)
        Console.WriteLine("--- Standard sort")
        For Each s In arr
            Console.WriteLine(s)
        Next

        Array.Sort(arr, CaseInsensitiveComparer.Default)
        Console.WriteLine("--- Sort using CaseInsensitiveComparer.Default")
        For Each s In arr
            Console.WriteLine(s)
        Next

        Array.Sort(arr, New CaseInsensitiveComparerVB6())
        Console.WriteLine("--- Sort using CaseInsensitiveComparerVB6")
        For Each s In arr
            Console.WriteLine(s)
        Next
    End Sub

    ' this procedure demonstrates the ICloneable interface

    Sub TestICloneable()
        ' Define an employee and his boss.
        Dim joe As New Employee("Joe", "Doe")
        Dim robert As New Employee("Robert", "Smith")
        joe.Boss = robert

        ' Clone it û The Clone method returns an object,
        ' thus you need DirectCast if Option Strict is On.
        Dim joe2 As Employee = DirectCast(joe.Clone, Employee)

        ' prove that all properties were copied
        Console.WriteLine(joe2.FirstName & " " & joe2.LastName _
            & ", whose boss is " & joe2.Boss.FirstName & " " & joe2.Boss.LastName)
        ' => Cloned object: Joe Doe, whose boss is Robert Smith
    End Sub

    ' this procedure proves that Clone does shallow copy

    Sub TestICloneable2()
        ' Define an employee and its boss
        Dim joe As New Employee("Joe", "Doe")
        Dim robert As New Employee("Robert", "Smith")
        joe.Boss = robert
        ' Clone it
        Dim joe2 As Employee = CType(joe.Clone, Employee)
        ' Prove that the Employee object was cloned, but his boss wasn't.
        Console.WriteLine(joe Is joe2)                   ' => False
        Console.WriteLine(joe.Boss Is joe2.Boss)         ' => True
    End Sub

    ' this procedure shows a deep copy clone method

    Sub TestICloneable3()
        ' Define an employee and its boss
        Dim joe As New Employee2("Joe", "Doe")
        Dim robert As New Employee2("Robert", "Smith")
        joe.Boss = robert
        ' Clone it
        Dim joe2 As Employee2 = CType(joe.Clone, Employee2)
        ' Prove that we clone the entire object graph.
        Console.WriteLine(joe Is joe2)                   ' => False
        Console.WriteLine(joe.Boss Is joe2.Boss)         ' => False
    End Sub

    ' this procedure tests a strong-typed Clone method

    Sub TestICloneable4()
        ' Define an employee and its boss
        Dim joe As New Employee3("Joe", "Doe")
        Dim robert As New Employee3("Robert", "Smith")
        joe.Boss = robert
        ' Clone it - note that no unboxing occurs here.
        Dim joe2 As Employee3 = joe.Clone
        ' Prove that we clone the entire object graph.
        Console.WriteLine(joe Is joe2)                   ' => False
        Console.WriteLine(joe.Boss Is joe2.Boss)         ' => False
    End Sub

    ' this procedure demonstrates the IEnumerable and IEnumerator interfaces.

    Sub TestIEnumerable()
        Dim msg As String = "Please, split this into individual words!"
        Dim o As Object
        For Each o In New WordParser(msg)
            Console.WriteLine(o)
        Next
    End Sub

    ' this procedure tests direct interaction with the GetEnumerator function

    Sub TestGetEnumerator()
        Dim f As System.IO.FileInfo

        ' enumerate all files in that directory tree
        For Each f In New FileTree("C:\Docs")
            Console.WriteLine(f.FullName)
        Next
    End Sub

End Module