C#教程之WebApi实现单个文件的上传下载

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C#教程之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         [HttpGet]
 5         public void DownloadFile()
 6         {
 7             var request = HttpContext.Current.Request;
 8             NameValueCollection nvCollection = request.Params;
 9             string fileName = nvCollection.GetValues("fileName")[0];
10             string filePath = Path.Combine(HttpContext.Current.Server.MapPath("~/App_Data/"), fileName);
11             if (File.Exists(filePath))
12             {
13                 HttpResponse response = HttpContext.Current.Response;
14                 response.Clear();
15                 response.ClearHeaders();
16                 response.ClearContent();
17                 response.Buffer = true;
18                 response.AddHeader("content-disposition", string.Format("attachment; FileName={0}", fileName));
19                 response.Charset = "GB2312";
20                 response.ContentEncoding = Encoding.GetEncoding("GB2312");
21                 response.ContentType = MimeMapping.GetMimeMapping(fileName);
22                 response.WriteFile(filePath);
23                 response.Flush();
24                 response.Close();
25             }
26         }

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：https://www.cnblogs.com/landeanfen/p/5177176.html

Demo下载：https://pan.baidu.com/s/1zV1-4WvrP3ZTWwTDFAmExQ

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