FileUpload is not passing the pro code file Behind

I'm doing some tests to upload any file and save it to a physical folder, but even with the file loaded on the screen, the same is not happening in ID / value:

Example:

Followingcodes:

aspx:

<divstyle="font-family: Arial">
                            <asp:FileUpload ID="FileUpload1" runat="server" />
                            <asp:Button ID="Button1" runat="server" Text="Upload"
                                OnClick="Button1_Click" />
                            <br />
                            <br />
                            <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False"
                                OnRowCommand="GridView1_RowCommand" BackColor="White"
                                BorderColor="#CC9966" BorderStyle="None"
                                BorderWidth="1px" CellPadding="4">
                                <Columns>
                                    <asp:TemplateField HeaderText="File" ShowHeader="False">
                                        <ItemTemplate>
                                            <asp:LinkButton ID="LinkButton1" runat="server"
                                                CausesValidation="False"
                                                CommandArgument='<%# Eval("File") %>'
                                                CommandName="Download" Text='<%# Eval("File") %>'>
                                            </asp:LinkButton>
                                        </ItemTemplate>
                                    </asp:TemplateField>
                                    <asp:BoundField DataField="Size" HeaderText="Size in Bytes" />
                                    <asp:BoundField DataField="Type" HeaderText="File Type" />
                                </Columns>
                                <FooterStyle BackColor="#FFFFCC" ForeColor="#330099" />
                                <HeaderStyle BackColor="#990000" Font-Bold="True"
                                    ForeColor="#FFFFCC" />
                                <PagerStyle BackColor="#FFFFCC" ForeColor="#330099"
                                    HorizontalAlign="Center" />
                                <RowStyle BackColor="White" ForeColor="#330099" />
                                <SelectedRowStyle BackColor="#FFCC66" Font-Bold="True"
                                    ForeColor="#663399" />
                                <SortedAscendingCellStyle BackColor="#FEFCEB" />
                                <SortedAscendingHeaderStyle BackColor="#AF0101" />
                                <SortedDescendingCellStyle BackColor="#F6F0C0" />
                                <SortedDescendingHeaderStyle BackColor="#7E0000" />
                            </asp:GridView>
                        </div>

aspx.cs

  protected void Button1_Click(object sender, EventArgs e)
    {
        if (FileUpload1.HasFile)
        {
            string fileName = FileUpload1.FileName;
            FileUpload1.PostedFile
                .SaveAs(Server.MapPath("~/Downloads/") + fileName);
        }

        DataTable dt = new DataTable();
        dt.Columns.Add("File");
        dt.Columns.Add("Size");
        dt.Columns.Add("Type");

        foreach (string strfile in Directory.GetFiles(Server.MapPath("~/Downloads")))
        {
            FileInfo fi = new FileInfo(strfile);
            dt.Rows.Add(fi.Name, fi.Length.ToString(),
                GetFileTypeByExtension(fi.Extension));
        }

        GridView1.DataSource = dt;
        GridView1.DataBind();
    }

    private string GetFileTypeByExtension(string fileExtension)
    {
        switch (fileExtension.ToLower())
        {
            case ".docx":
            case ".doc":
                return "Microsoft Word Document";
            case ".xlsx":
            case ".xls":
                return "Microsoft Excel Document";
            case ".txt":
                return "Text Document";
            case ".jpg":
            case ".png":
                return "Image";
            default:
                return "Unknown";
        }
    }


    protected void GridView1_RowCommand(object sender,
     GridViewCommandEventArgs e)
    {
        Response.Clear();
        Response.ContentType = "application/octet-stream";
        Response.AppendHeader("Content-Disposition", "filename="
            + e.CommandArgument);
        Response.TransmitFile(Server.MapPath("~/Data/")
            + e.CommandArgument);
        Response.End();
    }
}