ASP.NET 使用HTML file控件进行文件上传

第一种：

 <form id="form1"enctype="multipart/form-data" action="Default.aspx" method="post" >
 <input type="button" value="添加附件" onclick="addAttachment()" />  
    <div id="divAttachment">  
    </div>  
   <input type="submit"  value="提交"/>
</form>

JS：

      <script language="javascript">
    function addAttachment() {  
            var div = document.createElement("div");  
            var input = document.createElement("input");  
            input.setAttribute("type", "file");  
            input.setAttribute("name", "file");  
            input.setAttribute("runat", "server");
            input.setAttribute("size", "50");  
            div.appendChild(input);  
         
            var btnRemove = document.createElement("a");  
            btnRemove.setAttribute("href", "#");  
            btnRemove.innerText = "删除";  
            btnRemove.setAttribute("onclick", "removeAttachment(this)");    
            btnRemove.setAttribute("style", "text-decoration: none");  
            var span = document.createElement("span");  
            span.setAttribute("style", "padding-left: 5px");  
            span.appendChild(btnRemove);  
            div.appendChild(span);  
            document.getElementById("divAttachment").appendChild(div);  
        }  
        function removeAttachment(ctrl) {  
            while (ctrl.tagName != "DIV") {  
           
                ctrl = ctrl.parentNode;  
            }  
            ctrl.parentNode.removeChild(ctrl);  
        }  
      
 </script>

后台代码：

 protected void Page_Load(object sender, EventArgs e)
    {

        if (!Page.IsPostBack) {
            System.Web.HttpFileCollection files = Request.Files;

            for (int fileCount = 0; fileCount < files.Count; fileCount++)
            {

                System.Web.HttpPostedFile postedfile = files[fileCount];
                int size = postedfile.ContentLength;
                if (size <= 8388608)
                {
                    string fileName = System.IO.Path.GetFileName(postedfile.FileName);
                    if (!String.IsNullOrEmpty(fileName))
                    {

                        string fileExtension = System.IO.Path.GetExtension(fileName);    //获取文件类型  

                        //上传目录  
                        string directory = Server.MapPath("upload");
                        //文件全路径  
                        string path = directory + "\" + fileName;

                        //判断目录是否存在  
                        if (!Directory.Exists(directory))
                        {
                            Directory.CreateDirectory(directory);
                        }
                        //文件存在就删除文件  
                        if (File.Exists(path))
                        {
                            File.Delete(path);
                        }
                        //上传到服务器的路径  

                        postedfile.SaveAs(path);
                    }
                }
                else if (size > 8388608)
                {
                    Response.Write("<script>alert('上传文件不得超过8M');</script>");

                }
            }  
        
        }
   }

第二种：

使用asp.net的服务器控件 BUTTON按钮进行提交

<form id="form1" runat="server"  enctype="multipart/form-data" action="Default.aspx" method="post" >

 <input type="button" value="添加附件" onclick="addAttachment()" />  
 <div id="divAttachment">  
 </div>  
 <asp:Button runat="server" ID="button1" Text="提交" OnClick="sub_Fun" />
 </form>

上面JS中去掉

input.setAttribute("runat", "server");
后台代码添加一个 public void sub_Fun(object sender, EventArgs e){}函数即可。