ASP.NET การอ้างถึง Control ใน MasterPage

ใน MasterPage

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        If Not Me.Page.IsPostBack Then
            Dim A1() As String = {"Food", "Drinks", "Dessert"}
            DropDownList1.DataSource = A1
            DropDownList1.DataBind()
        End If
    End Sub

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Code ในหน้า TestPage

    Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim M1 As MasterPage = Me.Master
        Dim dx As DropDownList = M1.FindControl("DropDownList1")
        TextBox2.Text = dx.SelectedValue
    End Sub