[VB.NET]MDI形式でDLLを呼び出すには

    Public Interface IMosaMosaAA
        Sub MakiMakiLove()
    End Interface

    Public Class Form1 : Inherits System.Windows.Forms.Form : Implements IMosaMosaAA
        Public Sub MakiMakiLove() Implements IMosaMosaAA.MakiMakiLove
            MessageBox.Show("サラマンダーより……はやーい！")
        End Sub

        Private Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
            Dim hForm2 As New Form2()

            Me.IsMdiContainer = True
            hForm2.MdiParent = Me
            hForm2.Show()
        End Sub
    End Class

    Public Class Form2 : Inherits System.Windows.Forms.Form
        Private Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
            Dim hParentForm As Form = Me.MdiParent

            If TypeOf hParentForm Is IMosaMosaAA Then
                DirectCast(hParentForm, IMosaMosaAA).MakiMakiLove()
            End If
        End Sub
    End Class