最近,我将我的WPF应用程序(.NET 4.7)迁移到了.Net Core 3.1。它的大部分功能都能够正常工作,除了我无法生成/添加EF Core迁移。
我使用以下帖子中的依赖注入将我的dbContext
/ EF Core集成起来:
- https://marcominerva.wordpress.com/2019/03/06/using-net-core-3-0-dependency-injection-and-service-provider-with-wpf/
- https://marcominerva.wordpress.com/2019/03/19/using-entity-framework-core-with-wpf-on-net-core-3-0/
数据库连接正常工作。但是,当我尝试通过输入以下命令来添加迁移:Add-Migration InitialMigration
时,我一直会收到以下错误:
无法创建类型为'MyDBContext'的对象。有关设计时支持的不同模式,请参见https://go.microsoft.com/fwlink/?linkid=851728
在Web应用程序中,这似乎是一个常见/已知的问题,并且可以通过在程序类中更改CreateHostBuilder
为BuildWebHost
来进行修复;https://dev59.com/HVMH5IYBdhLWcg3w4E7k
我还发现添加MigrationsAssembly
到options.UseSqlServer
中的其他帖子。
长话短说,我尝试了所有这些解决方案,但似乎都没有起作用。可能是因为我的应用程序不是Web应用程序(没有程序类,如BuildWebHost),而是WPF(Core)应用程序。
我的WPF应用程序的初始化代码如下:
App.xaml.cs
public partial class App : Application
{
private readonly IHost host;
public IServiceProvider ServiceProvider { get; private set; }
public IConfiguration Configuration { get; private set; }
public App()
{
host = Host.CreateDefaultBuilder()
.ConfigureServices((context, services) =>
{
ConfigureServices(services);
}).Build();
}
private void ConfigureServices(IServiceCollection services)
{
// services for DI...
services.AddDbContext<MyDbContext>
(options =>
options.UseSqlServer(
Configuration.GetConnectionString("SqlConnection")));
services.AddTransient<MainWindow>();
}
protected override void OnStartup(StartupEventArgs e)
{
var builder = new ConfigurationBuilder()
.SetBasePath(Directory.GetCurrentDirectory())
.AddJsonFile("appsettings.json", optional: false, reloadOnChange: true);
Configuration = builder.Build();
var serviceCollection = new ServiceCollection();
ConfigureServices(serviceCollection);
ServiceProvider = serviceCollection.BuildServiceProvider();
var mainWindow = ServiceProvider.GetRequiredService<MainWindow>();
mainWindow.Show();
}
protected override async void OnExit(ExitEventArgs e)
{
using (host)
{
await host.StopAsync(TimeSpan.FromSeconds(5));
}
base.OnExit(e);
}
}
MyDbContext.cs
public class MyDbContext : DbContext
{
public MyDbContext(DbContextOptions<MyDbContext> options) : base(options)
{
Database.Migrate();
}
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
// Zonnescherm Model
modelBuilder.Entity<Zonneschermen>().Property(e => e.BreedteZonnescherm).HasColumnType("decimal(17,2)");
modelBuilder.Entity<Zonneschermen>().Property(e => e.UitvalDoek).HasColumnType("decimal(17,2)");
modelBuilder.Entity<Zonneschermen>().Property(e => e.ArmLengte).HasColumnType("decimal(17,2)");
// ScreenRegels Model
modelBuilder.Entity<ScreenRegels>().Property(e => e.Breedte).HasColumnType("decimal(17,2)");
modelBuilder.Entity<ScreenRegels>().Property(e => e.Hoogte).HasColumnType("decimal(17,2)");
modelBuilder.Entity<ScreenRegels>().Property(e => e.DraaistangLengte).HasColumnType("decimal(17,2)");
// Seed
modelBuilder.Entity<Instellingen>().HasData(
// seeding...
);
// Seed
modelBuilder.Entity<ZonneschermInstellingen>().HasData(
// seeding...
);
// Seed
modelBuilder.Entity<ScreenInstellingen>().HasData(
// seeding...
);
}
public DbSet<Lamellen> Lamellen { get; set; }
public DbSet<LamellenRegels> LamellenRegels { get; set; }
public DbSet<Zonneschermen> Zonneschermen { get; set; }
public DbSet<ZonneschermInstellingen> ZonneschermInstellingen { get; set; }
public DbSet<Screens> Screens { get; set; }
public DbSet<ScreenRegels> ScreenRegels { get; set; }
public DbSet<ScreenInstellingen> ScreenInstellingen { get; set; }
public DbSet<Instellingen> Instellingen { get; set; }
}
有任何线索表明出了问题吗?