Blazor Server调用异步UserManager方法时出现Circuit错误

基于Blazor Server开发Web应用，使用IdentityCore管理用户。在Razor组件中用户输入账户数据后，通过依赖注入调用服务创建用户时出现异常。

异常信息 #

[13:56:45 ERR] An exception occurred while iterating over the results of a query for context type 'ProjectName.Data.Context.DataContext'.
System.InvalidOperationException: A second operation was started on this context instance before a previous operation completed. This is usually caused by different threads concurrently using the same instance of DbContext.
   at Microsoft.EntityFrameworkCore.Infrastructure.Internal.ConcurrencyDetector.EnterCriticalSection()
   at Microsoft.EntityFrameworkCore.Query.Internal.SingleQueryingEnumerable`1.Enumerator.MoveNext()
System.InvalidOperationException: A second operation was started on this context instance before a previous operation completed. This is usually caused by different threads concurrently using the same instance of DbContext.
   at Microsoft.EntityFrameworkCore.Infrastructure.Internal.ConcurrencyDetector.EnterCriticalSection()
   at Microsoft.EntityFrameworkCore.Query.Internal.SingleQueryingEnumerable`1.Enumerator.MoveNext()

[13:56:45 WRN] Unhandled exception rendering component: Cannot access a disposed object.
System.ObjectDisposedException: Cannot access a disposed object.
   at Microsoft.AspNetCore.Components.RenderTree.ArrayBuilder`1.GrowBuffer(Int32 desiredCapacity)
   at Microsoft.AspNetCore.Components.Rendering.ComponentState.RenderIntoBatch(RenderBatchBuilder batchBuilder, RenderFragment renderFragment, Exception& renderFragmentException)
   at Microsoft.AspNetCore.Components.RenderTree.Renderer.ProcessRenderQueue()

[13:56:45 WRN] Unhandled exception rendering component: Cannot access a disposed object.
Object name: 'UserManager`1'.
System.ObjectDisposedException: Cannot access a disposed object.
Object name: 'UserManager`1'.
   at Microsoft.AspNetCore.Identity.UserManager`1.ThrowIfDisposed()
   at Microsoft.AspNetCore.Identity.UserManager`1.get_SupportsUserLockout()
   at Microsoft.AspNetCore.Identity.UserManager`1.CreateAsync(TUser user)
   at ProjectName.Service.Services.UserService.CreateUser(AppUser user) in C:\Users\erikm\source\repos\ProjectName\ProjectName.Service\Services\UserService.cs:line 66
   at ProjectName.Web.Pages.Employee.CompanyEmployees.CreateHandler(GridCommandEventArgs arg) in C:\Users\erikm\source\repos\ProjectName\ProjectName.Web\Pages\Employee\CompanyEmployees.razor:line 67
   at Microsoft.AspNetCore.Components.ComponentBase.CallStateHasChangedOnAsyncCompletion(Task task)
   at Telerik.Blazor.Components.Common.TableGridBase`2.InvokeEventAsync(EventCallback`1 event, TableCommandEventArgs args)
   at Telerik.Blazor.Components.Common.TableGridBase`2.InvokeCreateEventAsync(TableCommandEventArgs args)
   at Telerik.Blazor.Components.Common.TableGridBase`2.InvokeSaveEventAsync(TableCommandEventArgs args)
   at Telerik.Blazor.Components.Common.TableGridBase`2.ExecuteSaveCommandAsync(TableCommandEventArgs args)
   at Telerik.Blazor.Components.Common.TableGridBase`2.ExecuteValidatedCommand(TableCommandEventArgs args)
   at Telerik.Blazor.Components.TelerikGrid`1.ExecuteValidatedCommand(TableCommandEventArgs args)
   at Telerik.Blazor.Components.Common.TableGridBase`2.ExecuteCommand(Object commandArgs)
   at Telerik.Blazor.Components.Common.Grid.GridEditForm`1.FireCommand(String name)
   at Telerik.Blazor.Components.Common.Grid.GridEditForm`1.Update()
   at Microsoft.AspNetCore.Components.ComponentBase.CallStateHasChangedOnAsyncCompletion(Task task)
   at Telerik.Blazor.Components.TelerikForm.OnSubmitHandler()
   at Microsoft.AspNetCore.Components.ComponentBase.CallStateHasChangedOnAsyncCompletion(Task task)
   at Microsoft.AspNetCore.Components.RenderTree.Renderer.GetErrorHandledTask(Task taskToHandle, ComponentState owningComponentState)

相关代码 #

Razor组件代码 #

[Inject]
private IUserService _userService { get; set; }

private async Task CreateHandler(GridCommandEventArgs arg)
{
    if (arg.Item is AppUser user)
    {
        user.CompanyId = Company.Id;
        user.UserName = user.Email;
        await _userService.CreateUser(user);
    }
}

服务层代码 #

private readonly UserManager<AppUser> _userManager;
private readonly IDbContextFactory<DataContext> _dataContextFactory;
public UserService(UserManager<AppUser> userManager, IDbContextFactory<DataContext> dataContextFactory)
{
    _userManager = userManager;
    _dataContextFactory = dataContextFactory;
}

public async Task<AppUser?> CreateUser(AppUser user)
{
    IdentityResult result = await _userManager.CreateAsync(user);
    return result.Succeeded ? user : null;
}

Program.cs配置代码 #

var connectionString = builder.Configuration.GetConnectionString("DefaultConnection") ?? throw new InvalidOperationException("Connection string 'DefaultConnection' not found.");
builder.Services.AddDbContextFactory<DataContext>(options =>
{
    options.UseSqlServer(connectionString, sqlServerOptionsAction: sqlOptions =>
    {
        sqlOptions.EnableRetryOnFailure();
    });
});

builder.Services.AddIdentity<AppUser, AppRole>(options =>
    {
        options.SignIn.RequireConfirmedAccount = false;
    })
    .AddEntityFrameworkStores<DataContext>()
    .AddDefaultTokenProviders();

builder.Services.AddTransient<IUserService, UserService>();

环境：.NET 7.0，所有相关包均为7.0.0版本，期望在服务层异步创建用户。

解决方案 #

问题根源在于UserManager依赖的DbContext生命周期与当前配置不匹配：使用AddDbContextFactory注册上下文工厂，但AddEntityFrameworkStores默认使用Scoped生命周期的DbContext实例，Blazor Server组件生命周期较长，易引发并发操作或上下文提前释放问题。

步骤1：修改Identity配置，使用DbContext工厂 #

替换默认的UserManager注册逻辑，让它通过IDbContextFactory创建独立的上下文实例：

var connectionString = builder.Configuration.GetConnectionString("DefaultConnection") ?? throw new InvalidOperationException("Connection string 'DefaultConnection' not found.");
builder.Services.AddDbContextFactory<DataContext>(options =>
{
    options.UseSqlServer(connectionString, sqlServerOptionsAction: sqlOptions =>
    {
        sqlOptions.EnableRetryOnFailure();
    });
});

builder.Services.AddIdentity<AppUser, AppRole>(options =>
    {
        options.SignIn.RequireConfirmedAccount = false;
    })
    .AddDefaultTokenProviders();

// 自定义注册UserManager，使用DbContextFactory创建上下文
builder.Services.AddScoped<UserManager<AppUser>>(sp =>
{
    var contextFactory = sp.GetRequiredService<IDbContextFactory<DataContext>>();
    var userStore = new UserStore<AppUser, AppRole, DataContext>(contextFactory.CreateDbContext());
    var passwordHasher = sp.GetRequiredService<IPasswordHasher<AppUser>>();
    var userValidators = sp.GetServices<IUserValidator<AppUser>>();
    var passwordValidators = sp.GetServices<IPasswordValidator<AppUser>>();
    var keyNormalizer = sp.GetRequiredService<ILookupNormalizer>();
    var errors = sp.GetRequiredService<IdentityErrorDescriber>();
    var services = sp.GetRequiredService<IServiceProvider>();
    var logger = sp.GetRequiredService<ILogger<UserManager<AppUser>>>();

    return new UserManager<AppUser>(
        userStore, null, passwordHasher, userValidators, passwordValidators, 
        keyNormalizer, errors, services, logger);
});

builder.Services.AddTransient<IUserService, UserService>();

步骤2：验证异步操作正确性 #

确保所有异步方法都正确使用await（当前Razor组件和服务层代码已满足此要求），避免因未等待导致的上下文状态异常。

补充说明 #

• DbContext线程不安全，必须保证每个操作使用独立实例，IDbContextFactory是Blazor Server中管理上下文的推荐方式。
• 自定义UserManager注册逻辑后，每次调用UserManager方法都会获取全新的上下文实例，从根本上避免并发操作和上下文释放问题。

内容的提问来源于stack exchange，提问作者dasBaum