asp.net - 不断收到 SqlException:当 IDENTITY_INSERT 设置为 OFF 时,无法在表“电影”中插入标识列的显式值
问题描述
我正在开发一个程序,我将一个 excel 文件放到 SQL 数据库中。我正在使用 EPPlus -版本 4.5.2.1。导入 excel 文件 Movie 时,我不断收到错误消息。SqlException:当 IDENTITY_INSERT 设置为 OFF 时,无法在表“电影”中插入标识列的显式值。DbUpdateException:更新条目时发生错误。有关详细信息,请参阅内部异常。 HomeController.cs 中的 WebApplication14.Controllers.HomeController.Import(IFormFile 文件) + await _dbContext.SaveChangesAsync();
家庭控制器代码:
namespace WebApplication14.Controllers
{
public class HomeController : Controller
{
private readonly ApplicationDbContext _dbContext;
public HomeController(ApplicationDbContext dbContext)
{
_dbContext = dbContext;
}
public async Task<List<Movie>> Import(IFormFile file)
{
var list = new List<Movie>();
using (var stream = new MemoryStream())
{
await file.CopyToAsync(stream);
using (var package = new ExcelPackage(stream))
{
ExcelWorksheet worksheet = package.Workbook.Worksheets[0];
var rowcount = worksheet.Dimension.Rows;
var colcount = worksheet.Dimension.Columns;
for (int row = 2; row < rowcount; row++)
{
list.Add(new Movie
{
Id = int.Parse(worksheet.Cells[row, 1].Value.ToString().Trim()),
Title = worksheet.Cells[row, 2].Value.ToString().Trim(),
Genre = worksheet.Cells[row, 3].Value.ToString().Trim()
});
}
}
}
//SaveDataToDb(list);
_dbContext.Movie.AddRange(list);
await _dbContext.Database.ExecuteSqlCommandAsync(@"SET IDENTITY_INSERT [MovieList-1].[dbo].[Movie] ON");
await _dbContext.SaveChangesAsync();
await _dbContext.Database.ExecuteSqlCommandAsync(@"SET IDENTITY_INSERT [MovieList-1].[dbo].[Movie] OFF");
return list;
}
public IActionResult Index()
{
return View();
}
public IActionResult Privacy()
{
return View();
}
[ResponseCache(Duration = 0, Location = ResponseCacheLocation.None, NoStore = true)]
public IActionResult Error()
{
return View(new ErrorViewModel { RequestId = Activity.Current?.Id ?? HttpContext.TraceIdentifier });
}
}
}
模特电影
namespace WebApplication14.Models
{
public class Movie
{
public int Id { get; set; }
public string Title { get; set; }
public string Genre { get; set; }
}
}
DbContext 代码
namespace WebApplication14.Models
{
public class ApplicationDbContext : DbContext
{
public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options) : base(options)
{
}
public DbSet<Movie> Movie { get; set; }
}
}
我的迁移代码
public partial class MoviesToDb : Migration
{
protected override void Up(MigrationBuilder migrationBuilder)
{
migrationBuilder.CreateTable(
name: "Movie",
columns: table => new
{
Id = table.Column<int>(nullable: false)
.Annotation("SqlServer:Identity", "1, 1"),
Title = table.Column<string>(nullable: true),
Genre = table.Column<string>(nullable: true)
},
constraints: table =>
{
table.PrimaryKey("PK_Movie", x => x.Id);
});
}
protected override void Down(MigrationBuilder migrationBuilder)
{
migrationBuilder.DropTable(
name: "Movie");
}
}
}
启动代码
public class Startup
{
public Startup(IConfiguration configuration)
{
Configuration = configuration;
}
public IConfiguration Configuration { get; }
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
services.AddControllersWithViews();
services.AddDbContext<ApplicationDbContext>(options =>
options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));
services.Configure<CookiePolicyOptions>(options =>
{
// This lambda determines whether user consent for non-essential cookies is needed for a given request.
options.CheckConsentNeeded = context => true;
options.MinimumSameSitePolicy = SameSiteMode.None;
});
}
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
else
{
app.UseExceptionHandler("/Home/Error");
// The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
app.UseHsts();
}
app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseRouting();
app.UseAuthorization();
app.UseEndpoints(endpoints =>
{
endpoints.MapControllerRoute(
name: "default",
pattern: "{controller=Home}/{action=Index}/{id?}");
});
}
}
}
我的 AppSettings.Json 连接字符串
"ConnectionStrings": {
"DefaultConnection": "Server=localhost\\SQLEXPRESS;Database=MovieList-1;Trusted_Connection=True;MultipleActiveResultSets=true"
},
查看/首页/索引
@{
ViewData["Title"] = "Home Page";
}
<div class="text-center">
<h1 class="display-4">Welcome</h1>
<p>Learn about <a href="https://docs.microsoft.com/aspnet/core">building Web apps with ASP.NET Core</a>.</p>
<div class="container">
<form method="post" asp-controller="Home" asp-action="Import" enctype="multipart/form-data">
<input type="file" name="file" />
<button type="submit">Import From Excel</button>
</form>
</div>
</div>
解决方案
默认情况下,EF 会在每次操作后打开和关闭连接。这会导致 SqlConnection 被返回到连接池,并且每次从池中获取它时,它的状态都会被清除,包括删除临时表和重置会话级 SET 设置。
如果显式打开 DbContext 的连接(或启动事务),调用 SaveChanges() 时 IDENTITY_INSERT 设置应该仍然有效:
_dbContext.Database.OpenConnection();
_dbContext.Movie.AddRange(list);
await _dbContext.Database.ExecuteSqlCommandAsync(@"SET IDENTITY_INSERT [MovieList-1].[dbo].[Movie] ON");
await _dbContext.SaveChangesAsync();
await _dbContext.Database.ExecuteSqlCommandAsync(@"SET IDENTITY_INSERT [MovieList-1].[dbo].[Movie] OFF");
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