让ASP.NET的FileUpload控件支持浏览自动上传功能

FileUpload控件默认不支持服务端的ONCHANGE事件，此时用一种变通的方法

借用客户端的onchange事件，调用__doPostBack方法来用LinkButton的OnClick事件模拟一个事件触发的过程，具体代码如下：

客户端：

<asp:FileUpload ID="fuPhoto" onchange="javascript:__doPostBack('lbUploadPhoto','')"
                                runat="server" ToolTip="选择图片" />

<asp:LinkButton ID="lbUploadPhoto" runat="server" OnClick="lbUploadPhoto_Click"></asp:LinkButton>

后台代码：

        //自动上传事件
        protected void lbUploadPhoto_Click(object sender, EventArgs e)
        {
            fileUpload();
        }

        //从控件上传文件
        public void fileUpload()
        {
            if (fuPhoto.PostedFile != null && fuPhoto.PostedFile.ContentLength > 0)
            {
                string ext = System.IO.Path.GetExtension(fuPhoto.PostedFile.FileName).ToLower();
                if (ext != ".jpg" && ext != ".jepg" && ext != ".bmp" && ext != ".gif")
                {
                    return;
                }
                string filename = "Image_" + DateTime.Now.ToString("yyyyMMddHHmmss") + ext;
                string path = "./UploadPhoto/" + filename;
                fuPhoto.PostedFile.SaveAs(Server.MapPath(path));
                Response.Redirect("ImageCut.aspx?Picurl=" + Server.UrlEncode(path));
            }
            else
            {
                //do some thing;
            }
        }