Creating Interfaces

As discussed in the In Depth section of this chapter, interfaces can act as specifications for class members; when you implement an interface, you also must implement all the specified members. There's an example on the CD-ROM named Interfaces that shows how this works; in this case, I create an interface named person that specifies two members: SetName and GetName. Then I implement that interface in a class named employee with the Implements keyword (which must come after Inherits statements and before any Dim statements):

Public Interface person
    Sub SetName(ByVal PersonName As String)
    Function GetName() As String
End Interface

Public Class employee
    Implements person
    Dim Name As String

    Sub SetName(ByVal PersonName As String) Implements person.SetName
        Name = PersonName
    End Sub

    Function GetName() As String Implements person.GetName
        Return Name
    End Function
End Class

Now I can create an object of the employee class and use it in code, as you see in the Interfaces example:

Public Class Form1
    Inherits System.Windows.Forms.Form
    'Windows Form Designer generated code

    Private Sub Button1_Click(ByVal sender As System.Object, _
        ByVal e As System.EventArgs) Handles Button1.Click
        Dim Edward As New employee()
        Edward.SetName("Edward")
        TextBox1.Text = "You created " & Edward.GetName()
    End Sub
End Class

You can see the results of this code in Figure 12.3.