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;
           }
       }