无法为 Net Core 3.1 WPF 应用程序创建类型为“DbContext”的对象

Question

我的 SqlLite 数据库迁移引发错误：

Microsoft.EntityFrameworkCore.Design.OperationException: Unable to create an object of type 'ProductDbContext'.

---> System.MissingMethodException: No parameterless constructor defined for type 'WpfApp1.Data.ProductDbContext'.

这是我的 DbContext

public class ProductDbContext : DbContext
{
    #region Constructor
    public ProductDbContext(DbContextOptions<ProductDbContext> options) : base(options)
    {
        Database.EnsureCreated();
    }

    #endregion
    #region Public properties
    public DbSet<Product> Products { get; set; }
    public DbSet<Category> Types { get; set; }
    #endregion
    #region Overridden methods
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.ApplyConfiguration(new ProductDbConfig());
        modelBuilder.ApplyConfiguration(new CategoryDbConfig());
        modelBuilder.Entity<Product>().HasData(GetProducts());
        base.OnModelCreating(modelBuilder);
    }

    private Product[] GetProducts()
    {
        // create seed data
    }
}

我有一个 App.xaml.cs 我在其中进行配置

public partial class App : Application
{
    #region Private members
    private readonly ServiceProvider serviceProvider;
    #endregion

    #region Constructor
    public App()
    {
        ServiceCollection services = new ServiceCollection();

        services.AddDbContext<ProductDbContext>(options =>
        {
            options.UseSqlite("Data Source = Product.db");
        });

        services.AddSingleton<MainWindow>();
        serviceProvider = services.BuildServiceProvider();
    }
    #endregion


    #region Event Handlers
    private void OnStartup(object s, StartupEventArgs e)
    {
        var mainWindow = serviceProvider.GetService<MainWindow>();
        mainWindow.Show();
    }
    #endregion
}

我尝试在我的 dbContext 中添加一个无参数构造函数。没用。 是什么导致了这个错误？以及如何解决这个问题？ 任何帮助表示赞赏！

Answer 1

在我的 Xamarin.Forms 应用程序中，我在 DbContext 类中以这种方式使用它

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        // Specify that we will use sqlite and the path of the database here
        var options = optionsBuilder
            .UseSqlite($"Data Source={SQLiteDatabasePath}");

        base.OnConfiguring(options);
    }

== 编辑 ==

我的基类中所有服务的单例构造：

        private static ETabberDb _DbContext;

        protected ETabberDb ETabberDbContext
        {
            get
            {
                if (_DbContext == null)
                {
                    var dbPath = DeviceService.GetSQLiteDatabasePath();

                    if (!File.Exists(dbPath))
                    {
                        File.Create(dbPath).Dispose();
                        new SQLite.SQLiteConnection(dbPath).Dispose();
                    }

                    ETabberDb.SQLiteDatabasePath = dbPath;

                    _DbContext = new ETabberDb();
                }

                return _DbContext;
            }
        }