有人能详解下 get ... end get set ... end set 语句的详细调用过程及使用原理之类的吗？新手不是很理解这个函数，谢谢！MSDN

Public Class Form1

    Dim firstName, lastName As String
    Public Property fullName() As String
        Get
            If lastName = "" Then
                Return firstName
            Else
                Return firstName & " " & lastName
            End If

        End Get
        Set(ByVal Value As String)
            Dim space As Integer = Value.IndexOf(" ")
            If space < 0 Then
                firstName = Value
                lastName = ""
            Else
                firstName = Value.Substring(0, space)
                lastName = Value.Substring(space + 1)
            End If
        End Set
    End Property

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        fullName = "Firstname LastName"
        MsgBox(fullName)
    End Sub
End Class