向已存在角色添加用户时任务被取消的问题排查

现有数据 #

角色表 #

用户表 #

错误信息 #

The Task is cancelled
at
Microsoft.AspNetCore.Identity.UserManager`1.d__116.MoveNext()
at Web.SampleData.d__2.MoveNext() in
SampleData.cs:line 118

相关代码 #

分配角色方法 #

public static async Task<IdentityResult> 
           AssignRoles(IServiceProvider services, 
           string email, string[] roles)
{
  IdentityResult result = new IdentityResult();
  UserManager<ApplicationUser> _userManager = 
    services.GetService<UserManager<ApplicationUser>>();
   ApplicationUser user = await 
         _userManager.FindByEmailAsync(email);
   result = await _userManager.AddToRolesAsync(user, roles);            
   return result;
}

完整种子数据初始化方法 #

public static void CreateParent(IServiceProvider 
                                serviceProvider)
{
    var context = new DBContext();// 
     serviceProvider.GetService<DBContext>();
      string[] roles = new string[] { "Parent" };
      foreach (string role in roles)
      {
        var roleStore = new RoleStore<IdentityRole>(context);
        if (!context.Roles.Any(r => r.Name == role))
           {
             roleStore.CreateAsync(new IdentityRole(role));
            }
        }
        
        var user = new ApplicationUser
        {
            FirstName = "Parent",
            LastName = "One",
            Email = "parentone@apps-Test.com",
            NormalizedEmail = "parentone@apps-Test.com",
            UserName = "parentone@apps-Test.com",
            NormalizedUserName = "parentone@apps-Test.com",
            PhoneNumber = "+111111111111",
            EmailConfirmed = true,
            PhoneNumberConfirmed = true,
            SecurityStamp = Guid.NewGuid().ToString("D")
        };

        var db = new DBContext();
        if (!db.Users.Any(u => u.UserName == user.UserName))
        {
            var password = new PasswordHasher<ApplicationUser>();
            var hashed = password.HashPassword(user, "Test12345!");
            user.PasswordHash = hashed;
            var userStore = new UserStore<ApplicationUser> 
            (context);
            var result = userStore.CreateAsync(user);

        }

        AssignRoles(serviceProvider, user.Email, roles);
        db.SaveChangesAsync();
    }

Startup.cs调用代码 #

public void Configure(IApplicationBuilder app, 
   IWebHostEnvironment env,IServiceProvider service)
{
        SampleData.CreateParent(service);

}

角色已成功创建，但将用户添加到角色时出现任务取消错误，用户未被添加到aspnetuseroles表，请求排查原因。

核心问题：异步方法未正确等待 #

所有调用的异步方法都未使用await关键字，导致任务在未完成时就被终止，触发任务取消：

• roleStore.CreateAsync(new IdentityRole(role))：创建角色的异步操作未等待，可能角色还未写入数据库就执行后续步骤
• userStore.CreateAsync(user)：创建用户的异步操作未等待，用户可能未持久化就尝试分配角色
• AssignRoles(serviceProvider, user.Email, roles)：分配角色的异步方法被当作同步方法调用，未等待完成
• db.SaveChangesAsync()：保存更改的异步操作未等待，数据未持久化就结束流程

次要问题：DbContext实例混乱 #

代码中多次自行创建DBContext实例（new DBContext()），而非从依赖注入获取，导致上下文状态不一致：

• 创建用户用的是新实例db，但写入用户用的是另一个实例context
• 不同上下文实例的操作无法共享状态，可能导致查询不到刚创建的用户/角色

解决步骤 #

1. 将种子方法改为异步，并正确等待所有异步操作 #

public static async Task CreateParentAsync(IServiceProvider serviceProvider)
{
    // 从DI获取DbContext，不要自行new
    var context = serviceProvider.GetService<DBContext>();
    string[] roles = new string[] { "Parent" };
    
    foreach (string role in roles)
    {
        var roleStore = new RoleStore<IdentityRole>(context);
        if (!context.Roles.Any(r => r.Name == role))
        {
            // 等待角色创建完成
            await roleStore.CreateAsync(new IdentityRole(role));
        }
    }
    
    var user = new ApplicationUser
    {
        FirstName = "Parent",
        LastName = "One",
        Email = "parentone@apps-Test.com",
        NormalizedEmail = "PARENTONE@APPS-TEST.COM", // 符合Identity默认大写规范化逻辑
        UserName = "parentone@apps-Test.com",
        NormalizedUserName = "PARENTONE@APPS-TEST.COM",
        PhoneNumber = "+111111111111",
        EmailConfirmed = true,
        PhoneNumberConfirmed = true,
        SecurityStamp = Guid.NewGuid().ToString("D")
    };

    // 使用同一个context实例查询用户
    if (!context.Users.Any(u => u.UserName == user.UserName))
    {
        var password = new PasswordHasher<ApplicationUser>();
        var hashed = password.HashPassword(user, "Test12345!");
        user.PasswordHash = hashed;
        var userStore = new UserStore<ApplicationUser>(context);
        // 等待用户创建完成
        await userStore.CreateAsync(user);
    }

    // 等待角色分配完成
    await AssignRoles(serviceProvider, user.Email, roles);
    // 等待保存更改完成
    await context.SaveChangesAsync();
}

2. 修改Startup.cs中的调用方式 #

public void Configure(IApplicationBuilder app, IWebHostEnvironment env, IServiceProvider service)
{
    // 异步执行种子数据，避免异步上下文问题
    SampleData.CreateParentAsync(service).GetAwaiter().GetResult();
    
    // 其他中间件配置...
}

3. 修正规范化名称 #

Identity默认会将NormalizedEmail和NormalizedUserName转为大写，手动设置时保持大写，避免后续查询（比如FindByEmailAsync）因大小写不匹配找不到用户。

内容的提问来源于stack exchange，提问作者dotnetdevcsharp