WebApi实现单个文件的上传下载

上传和下载是很常用的功能了，只有当用到的时候才发现不会写...，经过一番百度、筛选、整理修改后，实现了功能，下面简单的记录下实现方法。

一、上传功能

1.前端代码

上传文件 <input type="file" id="file" />
<input type="button" id="upload" value="上传文件" />

<script>
    //上传
    $("#upload").click(function () {
        var formdata = new formdata();
        var file = document.getelementbyid("file").files[0];
        formdata.append("fileinfo", file);
        $.ajax({
            url: "../api/file/uploadfile",
            type: "post",
            data: formdata,
            contenttype: false,//必须false才会自动加上正确的content-type
            processdata: false,//必须false才会避开jquery对 formdata 的默认处理，xmlhttprequest会对 formdata 进行正确的处理
            success: function (data) {
                alert(data);
            },
            error: function (data) {
                alert("上传失败！");
            }
        });
    });
</script>

2.后台代码

 1         /// <summary>
 2         /// 上传文件
 3         /// </summary>
 4         [httppost]
 5         public string uploadfile()
 6         {
 7             string result = string.empty;
 8             try
 9             {
10                 string uploadpath = httpcontext.current.server.mappath("~/app_data/");
11                 httprequest request = system.web.httpcontext.current.request;
12                 httpfilecollection filecollection = request.files;
13                 // 判断是否有文件
14                 if (filecollection.count > 0)
15                 {
16                     // 获取文件
17                     httppostedfile httppostedfile = filecollection[0];
18                     string fileextension = path.getextension(httppostedfile.filename);// 文件扩展名
19                     string filename = guid.newguid().tostring() + fileextension;// 名称
20                     string filepath = uploadpath + httppostedfile.filename;// 上传路径
21                     // 如果目录不存在则要先创建
22                     if (!directory.exists(uploadpath))
23                     {
24                         directory.createdirectory(uploadpath);
25                     }
26                     // 保存新的文件
27                     while (file.exists(filepath))
28                     {
29                         filename = guid.newguid().tostring() + fileextension;
30                         filepath = uploadpath + filename;
31                     }
32                     httppostedfile.saveas(filepath);
33                     result = "上传成功";
34                 }
35             }
36             catch (exception)
37             {
38                 result = "上传失败";
39             }
40             return result;
41         }

 

二、下载功能

1.前端代码

 1 <form action="../api/file/downloadfile" method="get" id="form">
 2    下载文件 <input type="text" id="name" name="filename" value="222" />
 3 </form>
 4 <input type="button" id="download" value="下载文件" />
 5 
 6 <script>
 7     //下载
 8     $("#download").click(function () {
 9         var form = $("#form");
10         form.submit();
11     });
12 </script>

2.后台代码

 1         /// <summary>
 2         /// 下载文件
 3         /// </summary>
 4         /// <param name="filename"></param>
 5         [httpget]
 6         public void downloadfile(string filename)
 7         {
 8             string filepath = path.combine(httpcontext.current.server.mappath("~/app_data/"), filename);
 9             if (file.exists(filepath))
10             {
11                 httpresponse response = httpcontext.current.response;
12                 response.clear();
13                 response.clearheaders();
14                 response.clearcontent();
15                 response.buffer = true;
16                 response.addheader("content-disposition", string.format("attachment; filename={0}", filename));
17                 response.charset = "gb2312";
18                 response.contentencoding = encoding.getencoding("gb2312");
19                 response.contenttype = mimemapping.getmimemapping(filename);
20                 response.writefile(filepath);
21                 response.flush();
22                 response.close();
23             }
24         }

三、遇到的问题

1.写了个测试的html页，如何让程序运行时打开这个页面，在默认执行的homecontroler中添加重定向代码

httpcontext.response.redirect("html/index.html", true);

 2.跨域问题

当问题1中html页和后端程序分开部署时，就会产生跨域问题

可在web.config中进行如下配置

1   <system.webserver>
2     <httpprotocol>
3       <customheaders>
4         <add name="access-control-allow-origin" value="*"/>
5         <add name="access-control-allow-headers" value="x-requested-with,content-type,accept,origin"/>
6         <add name="access-control-allow-methods" value="get,post,put,delete,options"/>
7       </customheaders>    
8     </httpprotocol>
9   </system.webserver>

详情可阅读：

demo下载：https://pan.baidu.com/s/1zv1-4wvrp3ztwwtdfamexq