在转换所有表以开始使用标识列中的Guid类型后,我未能设定数据种子,因此我简化了大量代码以定位错误,并以一个种子类结束,如下所示:
public class SeedTest
{
private readonly MyDbContext _context;
public SeedTest(MyDbContext context)
{
_context = context;
}
public async Task SeedTest()
{
Values value1 = new Values
{
Id = Guid.Parse("29c48913-1b5c-47b8-g144-08d6d2273deb"),
ValueName = "value 1",
Created = DateTime.Now
};
_context.Values.Add(value1);
await _context.SaveChangesAsync();
}
public SeedTest()
{
}
}
这个类是从另一个调用的:
public interface IDatabaseInitializer
{
Task SeedAsync();
}
public class DatabaseInitializer : IDatabaseInitializer
{
public async Task SeedAsync()
{
SeedTest _seedTest = new SeedTest();
await _seedTest.SeedTest();
}
}
从startup.cs调用的
public class Startup
{
public IConfiguration Configuration { get; }
private readonly IHostingEnvironment _hostingEnvironment;
public Startup(IConfiguration configuration, IHostingEnvironment env)
{
Configuration = configuration;
_hostingEnvironment = env;
}
public void ConfigureServices(IServiceCollection services)
{
...
services.AddMyDbContext<MyDbContext>(options =>
options.UseSqlServer("ConnectionStrings:MyCn"));
...
// DB Seeding
services.AddTransient<IDatabaseInitializer, DatabaseInitializer>();
...
...
}
下面是如何从program.cs触发的
public class Program
{
public static void Main(string[] args)
{
var host = BuildWebHost(args);
using (var scope = host.Services.CreateScope())
{
var services = scope.ServiceProvider;
try
{
var databaseInitializer = services.GetRequiredService<IDatabaseInitializer>();
databaseInitializer.SeedAsync().Wait();
}
catch (Exception ex)
{
var logger = services.GetRequiredService<ILogger<Program>>();
logger.LogCritical(LoggingEvents.INIT_DATABASE, ex, LoggingEvents.INIT_DATABASE.Name);
}
}
host.Run();
}
public static IWebHost BuildWebHost(string[] args) =>
WebHost.CreateDefaultBuilder(args)
.UseStartup<Startup>()
.Build();
}
不幸的是,这个实现没有在数据库中植入任何数据,我能找到的唯一错误是在日志文件中,它说:
System.NullReferenceException:对象引用未设置为对象的实例。它指向SeedTest类的最后一行。
那么我到底做错了什么呢?
https://stackoverflow.com/questions/56677148
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