.NET Core 中实现文件上传

通过App, 网页或小程序上传文件到服务器上常见的一个功能，本文演示如何在 .NET Core 3 中实现文件上传的 WebApi。

为简化案例，突出服务端接收文件的基本功能，本例中并不会把上传的文件存入到数据库中，而是简单的保存在服务端的特定目录下。

实现 Post 方法

我们使用一个 Http Post 方法来接收用户上传的文件。在 .NET Core 中，要接收到文件，只需要将方法的参数设置为： IFormFile 类型即可。如下:

1 2	public async Task<ApiResult> UploadFile(IFormFile file) { }

文件上传到服务器上后，实际上存放在临时文件中的，我们通过 IFormFile 可以访问到该文件。在接下来的代码中，我们将建立一个本地目录，并为上传的文件准备要给随机的文件名，然后把上传的文件内容复制到新文件中。

[HttpPost]
public async Task<ApiResult> UploadFile(IFormFile file) {

    string fileName;

    ApiResult result = new ApiResult();


    _logger.LogDebug("UploadFile, fileName = {0}", file.FileName);

    try {
        var extension = "." + file.FileName.Split('.')[file.FileName.Split('.').Length - 1];
        fileName = DateTime.Now.Ticks + extension;

        var pathBuilt = Path.Combine(Directory.GetCurrentDirectory(), UPLOAD_FOLDER);

        if (!Directory.Exists(pathBuilt))
        {
            Directory.CreateDirectory(pathBuilt);
        }

        var path = Path.Combine(Directory.GetCurrentDirectory(), UPLOAD_FOLDER,
           fileName);

        
        using (var stream = new FileStream(path, FileMode.Create))
        {
            await file.CopyToAsync(stream);
        }

        result.Succ = true;

    }
    catch (Exception e)
    {
      _logger.LogDebug("fail to write file", e);
    }


    return result;
}

完整的代码

上传类的完整代码如下:

using System;
using System.IO;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Logging;
using System.Net.Http;
using System.Text.Json;
using System.Security.Cryptography; 
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Http.Features;

using WxServer.Model;
using WxServer.ApiVo;

namespace WxServer.Controllers
{

    
    
    [ApiController]
    [Route("/api/v1/product/check/photo")]
    public class ProductController : ControllerBase
    {

        const string UPLOAD_FOLDER = "Upload\\files";

        private readonly ILogger<ProductController> _logger;

        public ProductController(ILogger<ProductController> logger)
        {
            _logger = logger;
        }


        [HttpPost]
        public async Task<ApiResult> UploadFile(IFormFile file) {

            string fileName;

            ApiResult result = new ApiResult();


            _logger.LogDebug("UploadFile, fileName = {0}", file.FileName);

            try {
                var extension = "." + file.FileName.Split('.')[file.FileName.Split('.').Length - 1];
                fileName = DateTime.Now.Ticks + extension;

                var pathBuilt = Path.Combine(Directory.GetCurrentDirectory(), UPLOAD_FOLDER);

                if (!Directory.Exists(pathBuilt))
                {
                    Directory.CreateDirectory(pathBuilt);
                }

                var path = Path.Combine(Directory.GetCurrentDirectory(), UPLOAD_FOLDER,
                   fileName);

                
                using (var stream = new FileStream(path, FileMode.Create))
                {
                    await file.CopyToAsync(stream);
                }

                result.Succ = true;

            }
            catch (Exception e)
            {
              _logger.LogDebug("fail to write file", e);
            }

        
            return result;
        }
    }
}