Visual Basic.NET - Trabajar con varias ventanas

Dim frm As Form = Me.MdiChildren.FirstOrDefault(Function(x) TypeOf x Is FrmAgenda)

If frm IsNot Nothing Then

	frm.BringToFront()

	Return

End If

frm = New FrmAgenda

frm.MdiParent = Me

frm.Show()

Private Sub btnAgenda_Click(sender As Object, e As EventArgs) Handles btnAgenda.Click

    Dim form As Form

    Opened = False

    For Each form In Application.OpenForms()

        If form.Text = "Agenda Semanal - Citas Expertise" Then

            form.WindowState = FormWindowState.Maximized

            Opened = True

            Exit For

        End If

    Next

    If Opened = False Then

        Dim frm As New frmAgenda

        frm.Show()

    End If

End Sub

Dim FAgenda As Form = Application.OpenForms.Cast(Of Form)().FirstOrDefault(Function(x) TypeOf x Is FrmAgenda)

If FAgenda IsNot Nothing Then

	FAgenda.BringToFront()

	Return

End If

FAgenda = New FrmAgenda

FAgenda.Show()

Dim FAgenda As Form = Application.OpenForms.Cast(Of Form)().FirstOrDefault(Function(x) TypeOf x Is frmAgenda)

        If FAgenda IsNot Nothing Then

            FAgenda.WindowState = FormWindowState.Maximized

            Return

        End If

        FAgenda = New frmAgenda

        FAgenda.Show()