在ASP.NET Core 2.1的Application Startup上調用非靜態類來播種數據庫

Question

我試圖找出推薦的方法來調用一個類，該類將在ASP.NET Core 2.1應用程序中的應用程序啟動時啟動我的數據庫。

SeedDatabase.cs類不是靜態的，因為它依賴於在ConfigureServices中注冊的多個存儲庫，這些存儲庫是通過構造函數注入的。

我記得您以前在Configure方法中調用種子類的時候，但是我相信他們建議在2.1中調用它的方法是在Program.cs main方法中。 但是，如果我這樣做，則只有在類為靜態的情況下才起作用，在我的情況下，依賴項注入失敗。

Answer 1

按照以下方式更改Program.cs ：

public static void Main(string[] args) =>
    MainAsync(args).ConfigureAwait(false).GetAwaiter().GetResult();

public static async Task MainAsync(string[] args)
{
    var host = CreateWebHostBuilder(args).Build();
    // do something
    await host.RunAsync().ConfigureAwait(false);
}

public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
    WebHost.CreateDefaultBuilder(args)
        .UseStartup<Startup>();

在// do something部分中，您現在可以訪問已構建的主機對象，這也意味着您可以訪問服務。 您必須在這里使用服務定位器反模式，對於這種特定用例，實際上是可以的。

您可以采取多種方法。 您實際上可以在ConfigureServices注冊SeedDatabase類，然后在此處將其拉出，但這是非常不典型的。 它只會使用一次，因此並不是真正值得在您的服務集合中注冊的東西。 更好的方法是使該類成為靜態類，並更改實際執行工作的方法以將上下文作為參數。 然后，您可以執行以下操作：

using (var scope = host.Services.CreateScope())
{
    var context = scope.ServiceProvider.GetRequiredService<YourContext>();
    await SeedDatabase.SeedFoosAsync(context);
}

Answer 2

由於克里斯（Chris）的回答，我得到了餡餅：)我正在研究Pluralsight上的示例，而只是學習.NET Core。

這是有效的

using System;
using Microsoft.AspNetCore;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.DependencyInjection;
using BethanysPieShop.Models;

namespace BethanysPieShop
{
    public class Program
    {
        public static void Main(string[] args)
        {
            var host = CreateWebHostBuilder(args).Build();

            using (var scope = host.Services.CreateScope())
            {
                var services = scope.ServiceProvider;

                try
                {
                    var context = services.GetRequiredService<AppDbContext>();

                                        DbInitializer obj = new DbInitializer();
                obj.Seed(context);
                }
                catch (Exception)
                {
                    //we could log this in a real-world situation
                }

                host.Run();
            }
        }

        public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
            WebHost.CreateDefaultBuilder(args)
                .UseStartup<Startup>();
    }
}

這是我的DbInitializer類

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace BethanysPieShop.Models
{
    public class DbInitializer
    {
        public void Seed(AppDbContext context)
        {
            if (!context.Pies.Any())
            {
                context.AddRange(
                new Pie { Name = "Apple Pie", Price = 12.95M, ShortDescription = "Our famous apple pies!", LongDescription = "Icing carrot cake jelly-o cheesecake. Sweet roll marzipan marshmallow toffee brownie brownie candy tootsie roll. Chocolate cake gingerbread tootsie roll oat cake pie chocolate bar cookie dragée brownie. Lollipop cotton candy cake bear claw oat cake. Dragée candy canes dessert tart. Marzipan dragée gummies lollipop jujubes chocolate bar candy canes. Icing gingerbread chupa chups cotton candy cookie sweet icing bonbon gummies. Gummies lollipop brownie biscuit danish chocolate cake. Danish powder cookie macaroon chocolate donut tart. Carrot cake dragée croissant lemon drops liquorice lemon drops cookie lollipop toffee. Carrot cake carrot cake liquorice sugar plum topping bonbon pie muffin jujubes. Jelly pastry wafer tart caramels bear claw. Tiramisu tart pie cake danish lemon drops. Brownie cupcake dragée gummies.", ImageUrl = "https://gillcleerenpluralsight.blob.core.windows.net/files/applepie.jpg", IsPieOfTheWeek = true, ImageThumbnailUrl = "https://gillcleerenpluralsight.blob.core.windows.net/files/applepiesmall.jpg" },
                new Pie { Name = "Blueberry Cheese Cake", Price = 18.95M, ShortDescription = "You'll love it!", LongDescription = "Icing carrot cake jelly-o cheesecake. Sweet roll marzipan marshmallow toffee brownie brownie candy tootsie roll. Chocolate cake gingerbread tootsie roll oat cake pie chocolate bar cookie dragée brownie. Lollipop cotton candy cake bear claw oat cake. Dragée candy canes dessert tart. Marzipan dragée gummies lollipop jujubes chocolate bar candy canes. Icing gingerbread chupa chups cotton candy cookie sweet icing bonbon gummies. Gummies lollipop brownie biscuit danish chocolate cake. Danish powder cookie macaroon chocolate donut tart. Carrot cake dragée croissant lemon drops liquorice lemon drops cookie lollipop toffee. Carrot cake carrot cake liquorice sugar plum topping bonbon pie muffin jujubes. Jelly pastry wafer tart caramels bear claw. Tiramisu tart pie cake danish lemon drops. Brownie cupcake dragée gummies.", ImageUrl = "https://gillcleerenpluralsight.blob.core.windows.net/files/blueberrycheesecake.jpg", IsPieOfTheWeek = false, ImageThumbnailUrl = "https://gillcleerenpluralsight.blob.core.windows.net/files/blueberrycheesecakesmall.jpg" },
                new Pie { Name = "Cheese Cake", Price = 18.95M, ShortDescription = "Plain cheese cake. Plain pleasure.", LongDescription = "Icing carrot cake jelly-o cheesecake. Sweet roll marzipan marshmallow toffee brownie brownie candy tootsie roll. Chocolate cake gingerbread tootsie roll oat cake pie chocolate bar cookie dragée brownie. Lollipop cotton candy cake bear claw oat cake. Dragée candy canes dessert tart. Marzipan dragée gummies lollipop jujubes chocolate bar candy canes. Icing gingerbread chupa chups cotton candy cookie sweet icing bonbon gummies. Gummies lollipop brownie biscuit danish chocolate cake. Danish powder cookie macaroon chocolate donut tart. Carrot cake dragée croissant lemon drops liquorice lemon drops cookie lollipop toffee. Carrot cake carrot cake liquorice sugar plum topping bonbon pie muffin jujubes. Jelly pastry wafer tart caramels bear claw. Tiramisu tart pie cake danish lemon drops. Brownie cupcake dragée gummies.", ImageUrl = "https://gillcleerenpluralsight.blob.core.windows.net/files/cheesecake.jpg", IsPieOfTheWeek = false, ImageThumbnailUrl = "https://gillcleerenpluralsight.blob.core.windows.net/files/cheesecakesmall.jpg" },
                new Pie { Name = "Cherry Pie", Price = 15.95M, ShortDescription = "A summer classic!", LongDescription = "Icing carrot cake jelly-o cheesecake. Sweet roll marzipan marshmallow toffee brownie brownie candy tootsie roll. Chocolate cake gingerbread tootsie roll oat cake pie chocolate bar cookie dragée brownie. Lollipop cotton candy cake bear claw oat cake. Dragée candy canes dessert tart. Marzipan dragée gummies lollipop jujubes chocolate bar candy canes. Icing gingerbread chupa chups cotton candy cookie sweet icing bonbon gummies. Gummies lollipop brownie biscuit danish chocolate cake. Danish powder cookie macaroon chocolate donut tart. Carrot cake dragée croissant lemon drops liquorice lemon drops cookie lollipop toffee. Carrot cake carrot cake liquorice sugar plum topping bonbon pie muffin jujubes. Jelly pastry wafer tart caramels bear claw. Tiramisu tart pie cake danish lemon drops. Brownie cupcake dragée gummies.", ImageUrl = "https://gillcleerenpluralsight.blob.core.windows.net/files/cherrypie.jpg", IsPieOfTheWeek = false, ImageThumbnailUrl = "https://gillcleerenpluralsight.blob.core.windows.net/files/cherrypiesmall.jpg" },
                new Pie { Name = "Christmas Apple Pie", Price = 13.95M, ShortDescription = "Happy holidays with this pie!", LongDescription = "Icing carrot cake jelly-o cheesecake. Sweet roll marzipan marshmallow toffee brownie brownie candy tootsie roll. Chocolate cake gingerbread tootsie roll oat cake pie chocolate bar cookie dragée brownie. Lollipop cotton candy cake bear claw oat cake. Dragée candy canes dessert tart. Marzipan dragée gummies lollipop jujubes chocolate bar candy canes. Icing gingerbread chupa chups cotton candy cookie sweet icing bonbon gummies. Gummies lollipop brownie biscuit danish chocolate cake. Danish powder cookie macaroon chocolate donut tart. Carrot cake dragée croissant lemon drops liquorice lemon drops cookie lollipop toffee. Carrot cake carrot cake liquorice sugar plum topping bonbon pie muffin jujubes. Jelly pastry wafer tart caramels bear claw. Tiramisu tart pie cake danish lemon drops. Brownie cupcake dragée gummies.", ImageUrl = "https://gillcleerenpluralsight.blob.core.windows.net/files/christmasapplepie.jpg", IsPieOfTheWeek = false, ImageThumbnailUrl = "https://gillcleerenpluralsight.blob.core.windows.net/files/christmasapplepiesmall.jpg" },
                new Pie { Name = "Cranberry Pie", Price = 17.95M, ShortDescription = "A Christmas favorite", LongDescription = "Icing carrot cake jelly-o cheesecake. Sweet roll marzipan marshmallow toffee brownie brownie candy tootsie roll. Chocolate cake gingerbread tootsie roll oat cake pie chocolate bar cookie dragée brownie. Lollipop cotton candy cake bear claw oat cake. Dragée candy canes dessert tart. Marzipan dragée gummies lollipop jujubes chocolate bar candy canes. Icing gingerbread chupa chups cotton candy cookie sweet icing bonbon gummies. Gummies lollipop brownie biscuit danish chocolate cake. Danish powder cookie macaroon chocolate donut tart. Carrot cake dragée croissant lemon drops liquorice lemon drops cookie lollipop toffee. Carrot cake carrot cake liquorice sugar plum topping bonbon pie muffin jujubes. Jelly pastry wafer tart caramels bear claw. Tiramisu tart pie cake danish lemon drops. Brownie cupcake dragée gummies.", ImageUrl = "https://gillcleerenpluralsight.blob.core.windows.net/files/cranberrypie.jpg", IsPieOfTheWeek = false, ImageThumbnailUrl = "https://gillcleerenpluralsight.blob.core.windows.net/files/cranberrypiesmall.jpg" },
                new Pie { Name = "Peach Pie", Price = 15.95M, ShortDescription = "Sweet as peach", LongDescription = "Icing carrot cake jelly-o cheesecake. Sweet roll marzipan marshmallow toffee brownie brownie candy tootsie roll. Chocolate cake gingerbread tootsie roll oat cake pie chocolate bar cookie dragée brownie. Lollipop cotton candy cake bear claw oat cake. Dragée candy canes dessert tart. Marzipan dragée gummies lollipop jujubes chocolate bar candy canes. Icing gingerbread chupa chups cotton candy cookie sweet icing bonbon gummies. Gummies lollipop brownie biscuit danish chocolate cake. Danish powder cookie macaroon chocolate donut tart. Carrot cake dragée croissant lemon drops liquorice lemon drops cookie lollipop toffee. Carrot cake carrot cake liquorice sugar plum topping bonbon pie muffin jujubes. Jelly pastry wafer tart caramels bear claw. Tiramisu tart pie cake danish lemon drops. Brownie cupcake dragée gummies.", ImageUrl = "https://gillcleerenpluralsight.blob.core.windows.net/files/peachpie.jpg", IsPieOfTheWeek = false, ImageThumbnailUrl = "https://gillcleerenpluralsight.blob.core.windows.net/files/peachpiesmall.jpg" },
                new Pie { Name = "Pumpkin Pie", Price = 12.95M, ShortDescription = "Our Halloween favorite", LongDescription = "Icing carrot cake jelly-o cheesecake. Sweet roll marzipan marshmallow toffee brownie brownie candy tootsie roll. Chocolate cake gingerbread tootsie roll oat cake pie chocolate bar cookie dragée brownie. Lollipop cotton candy cake bear claw oat cake. Dragée candy canes dessert tart. Marzipan dragée gummies lollipop jujubes chocolate bar candy canes. Icing gingerbread chupa chups cotton candy cookie sweet icing bonbon gummies. Gummies lollipop brownie biscuit danish chocolate cake. Danish powder cookie macaroon chocolate donut tart. Carrot cake dragée croissant lemon drops liquorice lemon drops cookie lollipop toffee. Carrot cake carrot cake liquorice sugar plum topping bonbon pie muffin jujubes. Jelly pastry wafer tart caramels bear claw. Tiramisu tart pie cake danish lemon drops. Brownie cupcake dragée gummies.", ImageUrl = "https://gillcleerenpluralsight.blob.core.windows.net/files/pumpkinpie.jpg", IsPieOfTheWeek = true, ImageThumbnailUrl = "https://gillcleerenpluralsight.blob.core.windows.net/files/pumpkinpiesmall.jpg" },
                new Pie { Name = "Rhubarb Pie", Price = 15.95M, ShortDescription = "My God, so sweet!", LongDescription = "Icing carrot cake jelly-o cheesecake. Sweet roll marzipan marshmallow toffee brownie brownie candy tootsie roll. Chocolate cake gingerbread tootsie roll oat cake pie chocolate bar cookie dragée brownie. Lollipop cotton candy cake bear claw oat cake. Dragée candy canes dessert tart. Marzipan dragée gummies lollipop jujubes chocolate bar candy canes. Icing gingerbread chupa chups cotton candy cookie sweet icing bonbon gummies. Gummies lollipop brownie biscuit danish chocolate cake. Danish powder cookie macaroon chocolate donut tart. Carrot cake dragée croissant lemon drops liquorice lemon drops cookie lollipop toffee. Carrot cake carrot cake liquorice sugar plum topping bonbon pie muffin jujubes. Jelly pastry wafer tart caramels bear claw. Tiramisu tart pie cake danish lemon drops. Brownie cupcake dragée gummies.", ImageUrl = "https://gillcleerenpluralsight.blob.core.windows.net/files/rhubarbpie.jpg", IsPieOfTheWeek = true, ImageThumbnailUrl = "https://gillcleerenpluralsight.blob.core.windows.net/files/rhubarbpiesmall.jpg" },
                new Pie { Name = "Strawberry Pie", Price = 15.95M, ShortDescription = "Our delicious strawberry pie!", LongDescription = "Icing carrot cake jelly-o cheesecake. Sweet roll marzipan marshmallow toffee brownie brownie candy tootsie roll. Chocolate cake gingerbread tootsie roll oat cake pie chocolate bar cookie dragée brownie. Lollipop cotton candy cake bear claw oat cake. Dragée candy canes dessert tart. Marzipan dragée gummies lollipop jujubes chocolate bar candy canes. Icing gingerbread chupa chups cotton candy cookie sweet icing bonbon gummies. Gummies lollipop brownie biscuit danish chocolate cake. Danish powder cookie macaroon chocolate donut tart. Carrot cake dragée croissant lemon drops liquorice lemon drops cookie lollipop toffee. Carrot cake carrot cake liquorice sugar plum topping bonbon pie muffin jujubes. Jelly pastry wafer tart caramels bear claw. Tiramisu tart pie cake danish lemon drops. Brownie cupcake dragée gummies.", ImageUrl = "https://gillcleerenpluralsight.blob.core.windows.net/files/strawberrypie.jpg", IsPieOfTheWeek = false, ImageThumbnailUrl = "https://gillcleerenpluralsight.blob.core.windows.net/files/strawberrypiesmall.jpg" },
                new Pie { Name = "Strawberry Cheese Cake", Price = 18.95M, ShortDescription = "You'll love it!", LongDescription = "Icing carrot cake jelly-o cheesecake. Sweet roll marzipan marshmallow toffee brownie brownie candy tootsie roll. Chocolate cake gingerbread tootsie roll oat cake pie chocolate bar cookie dragée brownie. Lollipop cotton candy cake bear claw oat cake. Dragée candy canes dessert tart. Marzipan dragée gummies lollipop jujubes chocolate bar candy canes. Icing gingerbread chupa chups cotton candy cookie sweet icing bonbon gummies. Gummies lollipop brownie biscuit danish chocolate cake. Danish powder cookie macaroon chocolate donut tart. Carrot cake dragée croissant lemon drops liquorice lemon drops cookie lollipop toffee. Carrot cake carrot cake liquorice sugar plum topping bonbon pie muffin jujubes. Jelly pastry wafer tart caramels bear claw. Tiramisu tart pie cake danish lemon drops. Brownie cupcake dragée gummies.", ImageUrl = "https://gillcleerenpluralsight.blob.core.windows.net/files/strawberrycheesecake.jpg", IsPieOfTheWeek = false, ImageThumbnailUrl = "https://gillcleerenpluralsight.blob.core.windows.net/files/strawberrycheesecakesmall.jpg" }
            );
        }

        context.SaveChanges();
    }
}

}