Hide extra generated ASP.Net GridView after exporting to excel file using VB.Net

i have export excle file with the help of below code, but in my web page gridview genrated every time when loop executed.how i set visual false. please help mee.

HTML

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="True"></asp:GridView>

VB.net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        BindGrid()
    End If
End Sub

Private Function BindGrid() As DataTable
    Dim dt1 As DataTable = New DataTable()
    dt1.Columns.AddRange(New DataColumn(2) {New DataColumn("Id", GetType(Integer)), New DataColumn("Name", GetType(String)), New DataColumn("Country", GetType(String))})
    dt1.Rows.Add(1, "John Hammond", "United States")
    dt1.Rows.Add(2, "Mudassar Khan", "India")
    dt1.Rows.Add(3, "Suzanne Mathews", "France")
    dt1.Rows.Add(4, "Robert Schidner", "Russia")
    GridView1.DataSource = dt1
    GridView1.DataBind()
    ViewState("dt1") = dt1
    Return dt1
End Function

Protected Sub Export(ByVal sender As Object, ByVal e As EventArgs)
    Dim dt1 As DataTable = TryCast(ViewState("dt1"), DataTable)
    Dim j As Integer = 0

    While j < dt1.Rows.Count
        ExportToExcel()
        GridView1.Visible = False
        j = j + 1
    End While
End Sub

Private count As Integer = 0
Public Sub ExportToExcel()
    Dim a As String = "Book1"
    Dim path As String = Server.MapPath("~/File")
    If Not Directory.Exists(path) Then
        Directory.CreateDirectory(path)
    End If

    If File.Exists(path & "/File" & a & "_" & Convert.ToString(count) & ".xls") Then
        File.Delete(path & "/File" & a & "_" & Convert.ToString(count) & ".xls")
    End If

    Dim writer As StreamWriter = File.CreateText(path & "/File" & a & "_" & Convert.ToString(count) & ".xls")
    Using sw As StringWriter = New StringWriter()
        Using hw As HtmlTextWriter = New HtmlTextWriter(sw)
            Me.BindGrid()
            GridView1.RenderControl(hw)
            Response.Output.Write(sw.ToString())
            writer.Write(sw.ToString())
            writer.Flush()
            writer.Close()
            writer.Dispose()
            Response.Flush()
        End Using
    End Using
    count += 1
End Sub

Public Overrides Sub VerifyRenderingInServerForm(ByVal control As Control)
End Sub