前言

文件上传有两种方式：WEB上传和FTP上传。

• WEB上传就是通过点击网页中的“浏览”、“选定”、“上传”（或“确定”、“提交”）等按钮来上传文件的方式。精炼地说就是通过网页的功能上传文件。
• FTP[File Transfer Protocol]中文译为文件传输协议，是Internet上的另一项主要服务，这项服务让使用者能通过Internet来传输各式各样的文件。FTP上传的目标服务器有一个固定的FTP地址，这个地址可以是IP地址，也可以是域名地址。一般使用专用FTP工具软件来进行FTP上传，也可以使用IE浏览器。在使用FTP上传的时候，就像在我们的电脑磁盘上复制粘贴文件一样直观。

本文主要介绍WEB上传的几种方式。

一、文件上传与下载

1.单文件上传

1、相关代码

/// <summary>
/// 上传文件
/// </summary>
/// <param name="file">上传的文件</param>
/// <param name="fold">要存储的文件夹</param>
/// <returns></returns>
[HttpGet("Upload")]
public async Task<FileMessage> UploadFileAsync(IFormFile file, string fold)
{
    string fileName = file.FileName;
    string path = Directory.GetCurrentDirectory() + @"/Upload/" + fold + "/";
    if (!Directory.Exists(path))
    {
        Directory.CreateDirectory(path);
    }
    string argumentName = DateTime.Now.ToString("yyyyMMddHHmmssfff") + await FileHelp.GetFileSuffixAsync(file.FileName);
    string fileSize = Math.Round((decimal)file.Length / 1024, 2) + "k";
    string filePath = Path.Combine(path, argumentName);
    try
    {
        using (FileStream stream = new FileStream(filePath, FileMode.Create))
        {
            await file.CopyToAsync(stream);
        }
        return FileMessage.CreateNew(fileName, argumentName, fileSize, 1, "文件上传成功");
    }
    catch (Exception e)
    {
        return FileMessage.CreateNew(fileName, argumentName, fileSize, -1, "文件上传失败：" + e.Message);
    }
}

2、运行程序

2.多文件上传

1、相关代码

[HttpGet("UploadMul")]
public async Task<List<FileMessage>> UploadFilesAsync(IFormFileCollection files, string fold)
{
    string path = Directory.GetCurrentDirectory() + @"/Upload/" + fold + "/";
    if (!Directory.Exists(path))
    {
        Directory.CreateDirectory(path);
    }
    List<FileMessage> messages = new List<FileMessage>();
    foreach (var file in files)
    {
        string fileName = file.FileName;
        string argumentName = DateTime.Now.ToString("yyyyMMddHHmmssfff") + await FileHelp.GetFileSuffixAsync(file.FileName);
        string fileSize = Math.Round((decimal)file.Length / 1024, 2) + "k";
        string filePath = Path.Combine(path, argumentName);
        try
        {
            using (FileStream stream = new FileStream(filePath, FileMode.Create))
            {
                await file.CopyToAsync(stream);
            }
            messages.Add(FileMessage.CreateNew(fileName, argumentName, fileSize, 1, "文件上传成功"));
        }
        catch (Exception e)
        {
            messages.Add(FileMessage.CreateNew(fileName, argumentName, fileSize, -1, "文件上传失败，失败原因：" + e.Message));
        }
    }
    return messages;
}

2、运行程序

3.文件下载

1、相关代码

[Route("api/[controller]")]
[ApiController]
public class HomeController: ControllerBase
{
    private readonly string createName = "";
    private readonly IWebHostEnvironment _env;
    private readonly ILogger<HomeController> _logger;
    public HomeController(IWebHostEnvironment env,
        ILogger<HomeController> logger)
    {
        _env = env;
        _logger = logger;
    }
    
    /// <summary>
    /// 下载附件
    /// </summary>
    /// <param name="fileName">文件名称</param>
    /// <returns></returns>
    [HttpGet("download")]
    public async Task<FileStreamResult> Download([FromQuery] string fileName)
    {
        try
        {
            string rootPath = _env.ContentRootPath + @"/Upload/ManageProtocolFile";
            string filePath = Path.Combine(rootPath, fileName);
            var stream = System.IO.File.OpenRead(filePath);
            string contentType = await GetFileContentTypeAsync(fileName);
            _logger.LogInformation("用户:" + createName + "下载后台客户协议附件:" + request.FileName);
            return File(stream, contentType, fileName);
        }
        catch (Exception e)
        {
            _logger.LogError(e, "用户:" + createName + "下载后台客户协议附件出错，出错原因:" + e.Message);
            throw new Exception(e.ToString());
        }
    }
}

2、运行程序

相关类库

1、获取文件后缀

/// <summary>
/// 获取文件后缀
/// </summary>
/// <param name="fileName">文件名称</param>
/// <returns></returns>
public async static Task<string> GetFileSuffixAsync(string fileName)
{
    return await Task.Run(() =>
    {
        string suffix = Path.GetExtension(fileName);
        return suffix;
    });
}

2、获取ContentType属性

/// <summary>
/// 获取文件ContentType
/// </summary>
/// <param name="fileName">文件名称</param>
/// <returns></returns>
public async static Task<string> GetFileContentTypeAsync(string fileName)
{
    return await Task.Run(() =>
    {
        string suffix = Path.GetExtension(fileName);
        var provider = new FileExtensionContentTypeProvider();
        var contentType = provider.Mappings[suffix];
        return contentType;
    });
}

3、FileMessage

public class FileMessage
{
    /// <summary>
    /// 原文件名称
    /// </summary>
    public string FileName { get; set; }

    /// <summary>
    /// 附件名称(协议或其他要进行数据库保存与模型绑定的命名)
    /// </summary>
    public string ArgumentName { get; set; }

    /// <summary>
    /// 文件大小(KB)
    /// </summary>
    public string FileSize { get; set; }

    /// <summary>
    /// -1：上传失败 0：等待上传 1：已上传
    /// </summary>
    public int FileStatus { get; set; }

    /// <summary>
    /// 上传结果
    /// </summary>
    public string UploadResult { get; set; }

    /// <summary>
    /// 创建实例
    /// </summary>
    /// <param name="fileName">原文件名称</param>
    /// <param name="argumentName">(新)附件名称</param>
    /// <param name="fileSize">大小</param>
    /// <param name="fileStatus">文件状态</param>
    /// <returns></returns>
    public static FileMessage CreateNew(string fileName,
        string argumentName,
        string fileSize,
        int fileStatus,
        string uploadResult)
    {
        return new FileMessage()
        {
            FileName = fileName,
            ArgumentName = argumentName,
            FileSize = fileSize,
            FileStatus = fileStatus,
            UploadResult = uploadResult
        };
    }
}