使用 .NET Core 6 Web API 上传单个和多个文件

介绍

• .NET 提供了一个 IFormFile 接口，表示 HTTP 请求中传输的文件。
• 它还提供了许多属性，例如 ContentDisposition、ContentType、FileName、Headers、Name 和 Length。
• IFormFile 还提供了许多方法，例如复制请求流内容、打开请求流进行读取等等。

分步实施

步骤1

创建一个新的 .NET Core Web API。

第2步

安装以下 NuGet 包：

第 3 步

创建以下文件实体：

文件详细信息.cs

using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
namespace FileUpload.Entities
{
    [Table("FileDetails")]
    public class FileDetails
    {
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int ID { get; set; }
        public string FileName { get; set; }
        public byte[] FileData { get; set; }
        public FileType FileType { get; set; }
    }
}

文件上传模型

namespace FileUpload.Entities
{
    public class FileUploadModel
    {
        public IFormFile FileDetails { get; set; }
        public FileType FileType { get; set; }
    }
}

文件类型 

namespace FileUpload.Entities
{
    public enum FileType
    {
        PDF = 1,
        DOCX = 2
    }
}

第4步

接下来，Data 文件夹中的 DbContextClass.cs 类。

using FileUpload.Entities;
using Microsoft.EntityFrameworkCore;
namespace FileUpload.Data
{
    public class DbContextClass : DbContext
    {
        protected readonly IConfiguration Configuration;
        public DbContextClass(IConfiguration configuration)
        {
            Configuration = configuration;
        }
        protected override void OnConfiguring(DbContextOptionsBuilder options)
        {
            options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection"));
        }
        public DbSet<FileDetails> FileDetails { get; set; }
    }
}

第 5 步

它创建 IFileService 和 FileService 文件。

IFileService

using FileUpload.Entities;
namespace FileUpload.Services
{
    public interface IFileService
    {
        public Task PostFileAsync(IFormFile fileData, FileType fileType);
        public Task PostMultiFileAsync(List<FileUploadModel> fileData);
        public Task DownloadFileById(int fileName);
    }
}

FileService

using FileUpload.Data;
using FileUpload.Entities;
using Microsoft.EntityFrameworkCore;
namespace FileUpload.Services
{
    public class FileService : IFileService
    {
        private readonly DbContextClass dbContextClass;
        public FileService(DbContextClass dbContextClass)
        {
            this.dbContextClass = dbContextClass;
        }
        public async Task PostFileAsync(IFormFile fileData, FileType fileType)
        {
            try
            {
                var fileDetails = new FileDetails()
                {
                    ID = 0,
                    FileName = fileData.FileName,
                    FileType = fileType,
                };
                using (var stream = new MemoryStream())
                {
                    fileData.CopyTo(stream);
                    fileDetails.FileData = stream.ToArray();
                }
                var result = dbContextClass.FileDetails.Add(fileDetails);
                await dbContextClass.SaveChangesAsync();
            }
            catch (Exception)
            {
                throw;
            }
        }
        public async Task PostMultiFileAsync(List<FileUploadModel> fileData)
        {
            try
            {
                foreach(FileUploadModel file in fileData)
                {
                    var fileDetails = new FileDetails()
                    {
                        ID = 0,
                        FileName = file.FileDetails.FileName,
                        FileType = file.FileType,
                    };
                    using (var stream = new MemoryStream())
                    {
                        file.FileDetails.CopyTo(stream);
                        fileDetails.FileData = stream.ToArray();
                    }
                    var result = dbContextClass.FileDetails.Add(fileDetails);
                }
                await dbContextClass.SaveChangesAsync();
            }
            catch (Exception)
            {
                throw;
            }
        }
        public async Task DownloadFileById(int Id)
        {
            try
            {
                var file =  dbContextClass.FileDetails.Where(x => x.ID == Id).FirstOrDefaultAsync();
                var content = new System.IO.MemoryStream(file.Result.FileData);
                var path = Path.Combine(
                   Directory.GetCurrentDirectory(), "FileDownloaded",
                   file.Result.FileName);
                await CopyStream(content, path);
            }
            catch (Exception)
            {
                throw;
            }
        }
        public async Task CopyStream(Stream stream, string downloadPath)
        {
            using (var fileStream = new FileStream(downloadPath, FileMode.Create, FileAccess.Write))
            {
               await stream.CopyToAsync(fileStream);
            }
        }
    }
}

第 6 步

在控制器部分中创建 FilesController.cs。

using FileUpload.Entities;
using FileUpload.Services;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
namespace FileUpload.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class FilesController : ControllerBase
    {
        private readonly IFileService _uploadService;
        public FilesController(IFileService uploadService)
        {
            _uploadService = uploadService;
        }
        /// <summary>
        /// Single File Upload
        /// </summary>
        /// <param name="file"></param>
        /// <returns></returns>
        [HttpPost("PostSingleFile")]
        public async Task<ActionResult> PostSingleFile([FromForm] FileUploadModel fileDetails)
        {
            if(fileDetails == null)
            {
                return BadRequest();
            }
            try
            {
                await _uploadService.PostFileAsync(fileDetails.FileDetails, fileDetails.FileType);
                return Ok();
            }
            catch (Exception)
            {
                throw;
            }
        }
        /// <summary>
        /// Multiple File Upload
        /// </summary>
        /// <param name="file"></param>
        /// <returns></returns>
        [HttpPost("PostMultipleFile")]
        public async Task<ActionResult> PostMultipleFile([FromForm] List<FileUploadModel> fileDetails)
        {
            if (fileDetails == null)
            {
                return BadRequest();
            }
            try
            {
                await _uploadService.PostMultiFileAsync(fileDetails);
                return Ok();
            }
            catch (Exception)
            {
                throw;
            }
        }
        /// <summary>
        /// Download File
        /// </summary>
        /// <param name="file"></param>
        /// <returns></returns>
        [HttpGet("DownloadFile")]
        public async Task<ActionResult> DownloadFile(int id)
        {
            if (id < 1)
            {
                return BadRequest();
            }
            try
            {
                await _uploadService.DownloadFileById(id);
                return Ok();
            }
            catch (Exception)
            {
                throw;
            }
        }
    }
}

第 7 步

在 Program Class 和 DI Container 中配置一些服务。

using FileUpload.Data;
using FileUpload.Services;
var builder = WebApplication.CreateBuilder(args);
// Add services to the container.
builder.Services.AddControllers();
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();
builder.Services.AddDbContext<DbContextClass>();
builder.Services.AddScoped<IFileService, FileService>();
var app = builder.Build();
// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}
app.UseAuthorization();
app.MapControllers();
app.Run();

第 8 步

在 SQL Server 中创建一个新数据库并将其命名为 FileUploadDemo。

第 9 步

接下来，使用以下脚本创建 FileDetails 表。

USE [FileUploadDemo]
GO
/****** Object:  Table [dbo].[FileDetails]    Script Date: 10/1/2022 5:51:22 PM ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[FileDetails](
	[ID] [int] IDENTITY(1,1) NOT NULL,
	[FileName] [nvarchar](80) NOT NULL,
	[FileData] [varbinary](max) NOT NULL,
	[FileType] [int] NULL,
 CONSTRAINT [PK_FileDetails] PRIMARY KEY CLUSTERED
(
	[ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, OPTIMIZE_FOR_SEQUENTIAL_KEY = OFF) ON [PRIMARY]
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]
GO

第 10 步

将数据库连接放在 appsettings.json 文件中。

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "AllowedHosts": "*",
  "ConnectionStrings": {
    "DefaultConnection": "Data Source=DESKTOP-****;;Initial Catalog=FileUploadDemo;User Id=sa;Password=database;"
  }
}