Blazor WebAssembly文件上传MySQL失败：Blob长度为0求助

我在Blazor WebAssembly项目中尝试将文件上传至MySQL数据库，但Blob字段始终只存储长度为0的字节数组，相关代码如下，求排查问题：

Controller代码 #

[Route("api/[controller]")]
[ApiController]
public class FileController : Controller
{
    private readonly FileUploadDbContext _fileUploadDbContext;
    private readonly IFileUploadServices _fileUploadServices;
    public FileController(IFileUploadServices fileUploadServices, FileUploadDbContext fileUploadDbContext)
    {
        _fileUploadDbContext = fileUploadDbContext ?? throw new ArgumentNullException(nameof(fileUploadDbContext));
        _fileUploadServices = fileUploadServices;
    }

    [HttpGet]
    public async Task<ActionResult<IEnumerable<UploadFileInfo>>> Get()
    {
        await _fileUploadServices.GetUplaodFile();
        return Ok("file get");
    }

    [HttpPost]
    public async Task<ActionResult> Post(IFormFile formFile)
    {
        using (var ms = new MemoryStream())
        {
            formFile.CopyTo(ms);
            var fileBytes = ms.ToArray();
            string s = Convert.ToBase64String(fileBytes);
            // act on the Base64 data
            var fileinfo = new UploadFileInfo
            {
                Data = fileBytes,
                FileId = 1, //Ignore the 1, for testing purpose
                FileName = formFile.FileName,
            };
            await _fileUploadServices.UploadFiles(fileinfo);
            return Ok("file created");
        }
    }
}

Services代码 #

public class FileUploadServices : IFileUploadServices
{
    private readonly IDbContextFactory<FileUploadDbContext> _contextFactory;

    public FileUploadServices(IDbContextFactory<FileUploadDbContext> contextFactory)
    {
        _contextFactory = contextFactory;
    }

    public async Task UploadFiles(UploadFileInfo uploadFileInfos)
    {
        using (var context = _contextFactory.CreateDbContext())
        {
            context.fileUploadInfos.Add(uploadFileInfos);
            await context.SaveChangesAsync();
        }
    }

    public async Task<IList<UploadFileInfo>> GetUplaodFile()
    {
        using (var context = _contextFactory.CreateDbContext())
        {
            var uploadfiles = await context.fileUploadInfos.ToListAsync();
            return uploadfiles;
        }
    }
}

Model代码 #

public class UploadFileInfo
{
    [Key]
    public int FileId { get; set; }

    public string FileName { get; set; }
    public byte[] Data { get; set; }
}

Migration代码 #

public partial class mg1 : Migration
{
    /// <inheritdoc />
    protected override void Up(MigrationBuilder migrationBuilder)
    {
        migrationBuilder.AlterDatabase()
            .Annotation("MySQL:Charset", "utf8mb4");

        migrationBuilder.CreateTable(
            name: "fileUploadInfos",
            columns: table => new
            {
                FileId = table.Column<int>(type: "int", nullable: false)
                    .Annotation("MySQL:ValueGenerationStrategy", MySQLValueGenerationStrategy.IdentityColumn),
                FileName = table.Column<string>(type: "longtext", nullable: false),
                Data = table.Column<byte[]>(type: "longblob", nullable: false)
            },
            constraints: table =>
            {
                table.PrimaryKey("PK_fileUploadInfos", x => x.FileId);
            })
            .Annotation("MySQL:Charset", "utf8mb4");
    }

    /// <inheritdoc />
    protected override void Down(MigrationBuilder migrationBuilder)
    {
        migrationBuilder.DropTable(
            name: "fileUploadInfos");
    }
}

调试时发现读取后的字节数组为空，数据库Blob字段也显示为空，恳请帮忙排查问题。

排查关键点 #

• 前端请求格式验证：Blazor WASM上传文件必须使用multipart/form-data格式构造FormData，确保后端能正确接收IFormFile。如果前端未正确提交，formFile会是空对象，导致读取的字节数组长度为0。
• 添加IFormFile有效性判断：在Controller的Post方法开头增加校验：

  if (formFile == null || formFile.Length == 0)
  {
      return BadRequest("未上传有效文件");
  }
  

• 移除硬编码的主键值：Migration中已设置FileId为自增列，代码中手动设置FileId=1可能导致主键冲突，或EF Core内部逻辑异常，应删除该赋值，让数据库自动生成主键。
• 捕获保存异常：在UploadFiles方法中添加异常捕获，确认保存时是否有未被处理的错误：

  public async Task UploadFiles(UploadFileInfo uploadFileInfos)
  {
      using (var context = _contextFactory.CreateDbContext())
      {
          try
          {
              context.fileUploadInfos.Add(uploadFileInfos);
              await context.SaveChangesAsync();
          }
          catch (Exception ex)
          {
              // 日志记录或输出异常详情
              throw;
          }
      }
  }
  

• 确认上下文注入正确性：检查FileUploadDbContext的连接字符串是否指向目标数据库，避免操作了错误的数据库实例。

内容的提问来源于stack exchange，提问作者slipperyD