[asp.net] How to choose multiple files using File Upload Control?

default.aspx code

<asp:FileUpload runat="server" id="fileUpload1" Multiple="Multiple">
        </asp:FileUpload>
<asp:Button runat="server" Text="Upload Files" id="uploadBtn"/>

default.aspx.vb

Protected Sub uploadBtn_Click(sender As Object, e As System.EventArgs) Handles uploadBtn.Click
    Dim ImageFiles As HttpFileCollection = Request.Files
    For i As Integer = 0 To ImageFiles.Count - 1
    Dim file As HttpPostedFile = ImageFiles(i)
        file.SaveAs(Server.MapPath("Uploads/") & file.FileName) 
    Next       
End Sub