ASP.NET C#两个单个FileUpload一次只能从一个控件上载文件

<asp:FileUpload ID="FileUpload1" runat="server" />
<asp:FileUpload ID="FileUpload2" runat="server" />

protected void UploadButton_Click(object sender, EventArgs e)
{
    if (FileUpload1.HasFile)
    {
        string fileName = Path.GetFileName(FileUpload1.FileName);
        FileUpload1.SaveAs(Server.MapPath("~/Uploads/") + fileName);
    }
    if (FileUpload2.HasFile)
    {
        string fileName = Path.GetFileName(FileUpload2.FileName);
        FileUpload2.SaveAs(Server.MapPath("~/Uploads/") + fileName);
    }
}