SQL Server Express LocalDB环境下DbInitializer数据未填充到数据库问题

你当前的种子数据不生效是触发逻辑设计错误导致的，和懒加载、配置遗漏无关：

• Database.EnsureCreated() 方法仅在数据库完全不存在、首次创建时才返回true，只要你此前运行过一次程序、数据库已被创建（哪怕表中无任何数据），后续启动时EnsureCreated()都会返回false，直接跳过CreateDbIfNotExists方法，自然不会执行种子插入逻辑。
• 你在Main方法中提前创建了一个独立的服务Scope调用EnsureCreated()，和后续种子逻辑使用的不是同一个上下文实例，也可能存在状态不一致问题。
• 你将代码放到HomeController中能正常执行，是因为访问页面时手动触发了种子逻辑，不受EnsureCreated()返回值的限制。

第一步：修改Program.cs的触发逻辑 #

删除Main方法中多余的EnsureCreated()判断，直接调用初始化方法即可：

public static void Main(string[] args)
{
    var host = CreateHostBuilder(args).Build();
    // 直接调用初始化方法，不再做EnsureCreated返回值判断
    CreateDbIfNotExists(host);
    host.Run();
}

第二步：给DbInitializer增加重复数据校验 #

避免多次启动程序重复插入相同数据，修改Seed方法的逻辑，插入前先校验数据是否已存在：

public static void Seed(ApplicationDbContext context, IServiceProvider services)
{
    //  Seed roles
    RoleManager<IdentityRole> roleManager = services.GetRequiredService<RoleManager<IdentityRole>>();
    string[] roleNames = { "Traffic Manager", "Traffic Officer", "Driver" };
    foreach (var roleName in roleNames)
    {
        // 角色不存在才创建
        if (!roleManager.RoleExistsAsync(roleName).Result)
        {
            roleManager.CreateAsync(new IdentityRole() { Name = roleName }).Wait();
        }
    }

    //  Seed test users
    UserManager<IdentityUser> userManager = services.GetRequiredService<UserManager<IdentityUser>>();
    var testUsers = new List<(string Email, string Role)>
    {
        ("driver@testwebsite.com", "Driver"),
        ("officer@testwebsite.com", "Traffic Officer"),
        ("manager@testwebsite.com", "Traffic Manager")
    };
    foreach (var (email, role) in testUsers)
    {
        // 用户不存在才创建
        var user = userManager.FindByEmailAsync(email).Result;
        if (user == null)
        {
            user = new IdentityUser()
            {
                Email = email,
                UserName = email,
                EmailConfirmed = true,
                TwoFactorEnabled = false
            };
            userManager.CreateAsync(user).Wait();
            userManager.AddPasswordAsync(user, "Pa$$word1").Wait();
            userManager.AddToRoleAsync(user, role).Wait();
        }
    }

    // Seed fines，表为空才插入
    if (!context.Fines.Any())
    {
        var fine = new Fine[]
        {
            new Fine {
                FineID = Guid.NewGuid().ToString(),
                OfficerID = Guid.NewGuid().ToString(),
                DriverID = Guid.NewGuid().ToString(),
                LicensePlate = "CY4345",
                VehicleType = VehicleType.Car,
                Offense = OffenseType.Speeding,
                OffenseDetail = "85km/h in a 60 zone.",
                OffenseDate = DateTime.Parse("2017-08-10"),
                OffenseTime = DateTime.Parse("05:50"),
                Amount = 50.50m,
                Outstanding = true
            },
            new Fine {
                FineID = Guid.NewGuid().ToString(),
                OfficerID = Guid.NewGuid().ToString(),
                DriverID = Guid.NewGuid().ToString(),
                LicensePlate = "CA323566",
                VehicleType = VehicleType.Bus,
                Offense = OffenseType.Parking,
                OffenseDetail = "Parked on red line.",
                OffenseDate = DateTime.Parse("2018-01-20"),
                OffenseTime = DateTime.Parse("16:20"),
                Amount = 350.00m,
                Outstanding = true
            },
            new Fine {
                FineID = Guid.NewGuid().ToString(),
                OfficerID = Guid.NewGuid().ToString(),
                DriverID = Guid.NewGuid().ToString(),
                LicensePlate = "CY198450",
                VehicleType = VehicleType.Car,
                Offense = OffenseType.Speeding,
                OffenseDetail = "140km/h in a 100 zone.",
                OffenseDate = DateTime.Parse("2014-03-12"),
                OffenseTime = DateTime.Parse("09:15"),
                Amount = 500.00m,
                Outstanding = true
            },
            new Fine {
                FineID = Guid.NewGuid().ToString(),
                OfficerID = Guid.NewGuid().ToString(),
                DriverID = Guid.NewGuid().ToString(),
                LicensePlate = "CA321",
                VehicleType = VehicleType.Motorcycle,
                Offense = OffenseType.Speeding,
                OffenseDetail = "65km/h in a 40 zone.",
                OffenseDate = DateTime.Parse("2018-10-19"),
                OffenseTime = DateTime.Parse("15:00"),
                Amount = 250.00m,
                Outstanding = true
            },
            new Fine {
                FineID = Guid.NewGuid().ToString(),
                OfficerID = Guid.NewGuid().ToString(),
                DriverID = Guid.NewGuid().ToString(),
                LicensePlate = "CA974039",
                VehicleType = VehicleType.Car,
                Offense = OffenseType.DUI,
                OffenseDetail = "DUI of alcohol.",
                OffenseDate = DateTime.Parse("2016-11-11"),
                OffenseTime = DateTime.Parse("10:10"),
                Amount = 650.80m,
                Outstanding = false
            },
            new Fine {
                FineID = Guid.NewGuid().ToString(),
                OfficerID = Guid.NewGuid().ToString(),
                DriverID = Guid.NewGuid().ToString(),
                LicensePlate = "CY936503",
                VehicleType = VehicleType.Car,
                Offense = OffenseType.Parking,
                OffenseDetail = "Illegally parked on corner.",
                OffenseDate = DateTime.Parse("2015-06-21"),
                OffenseTime = DateTime.Parse("11:41"),
                Amount = 250.00m,
                Outstanding = true
            },
            new Fine {
                FineID = Guid.NewGuid().ToString(),
                OfficerID = Guid.NewGuid().ToString(),
                DriverID = Guid.NewGuid().ToString(),
                LicensePlate = "CA99840",
                VehicleType = VehicleType.Truck,
                Offense = OffenseType.Speeding,
                OffenseDetail = "100km/h in a 60 zone.",
                OffenseDate = DateTime.Parse("2016-06-21"),
                OffenseTime = DateTime.Parse("09:55"),
                Amount = 1500.00m,
                Outstanding = true
            },
        };
        context.Fines.AddRange(fine);
        context.SaveChanges();
    }
}

可选：强制重置数据 #

如果你需要重新生成所有种子数据，可先删除LocalDB对应的mdf/ldf文件，或者直接在SSMS中删除现有数据库，重新启动程序即可自动完成库表创建和数据播种。

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