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:

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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。

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[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:

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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;
}
}
}