相关疑难解决方法(0)

如何使用ASP.NET Core MVC内置依赖注入框架手动解析类型？

设置容器很容易:

public void ConfigureServices(IServiceCollection services)
{
    // ...

    services.AddTransient<ISomeService, SomeConcreteService>();
}

但是如何在ISomeService不进行注射的情况下解决？例如,我想这样做:

ISomeService service = services.Resolve<ISomeService>();

没有这样的方法IServiceCollection.

我是EF核心的新手,我正试图让它与我的asp.net核心项目一起工作.

startup.cs在尝试配置dbcontext以使用来自config的连接字符串时,我得到了上述错误.我正在关注本教程:https://docs.microsoft.com/en-us/aspnet/core/data/ef-mvc/intro

startup.cs中有问题的代码:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.SpaServices.Webpack;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using Microsoft.EntityFrameworkCore;
using tracV2.models;
using tracV2.data;

namespace tracV2
{
    public class Startup
    {
        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            // Add framework services.
            services.AddMvc();

            services.AddSingleton<IConfiguration>(Configuration);

            string conn = Configuration.GetConnectionString("optimumDB");

            services.AddDbContext<tracContext>(options => options.usesqlserver(conn));
        }

usesqlserver如果我将其直接放入上下文中,则会识别该方法:

using System; …

是否可以让我的ASP Core Web API确保使用EF Core将数据库迁移到最新的迁移？我知道这可以通过命令行完成,但我想以编程方式完成.

更新

根据Janshair Khan的回答,我提出了这个助手类:

using Microsoft.AspNetCore.Builder;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.DependencyInjection;
using MyWebApi.Models;

namespace MyWebApi
{
    public static class DataSeeder
    {
        public static void SeedData(this IApplicationBuilder app)
        {
            var context = app.ApplicationServices.GetService<MyContext>();

            if (!context.Database.EnsureCreated())
                context.Database.Migrate();
        }
    }
}

您可以通过以下Configure方法调用此方法Startup.cs:

app.SeedData();

似乎在Entity Framework 7中还没有对种子数据的原生支持(https://github.com/aspnet/EntityFramework/issues/629).

Microsoft提供的模板代码中没有DbMigrationsConfiguration类,没有Seed方法.

那么如何在使用Entity Framework 7 RC 1的ASP.NET MVC 6 Web应用程序中播种数据呢？

如何从代码中应用迁移

对于EF6工作代码

    Database.SetInitializer<CmContext>(null);
    var settings = new MigrationsConfiguration();
    var migrator = new DbMigrator(settings);
    migrator.Update();

如何在EF Core中制作类似的？

我正在使用 ASP.NET Core 6 编写一个网站。它最初是来自 YouTube 的 .NET Core 3 教程。所以我面临迁移问题。\n这里，我有一个 DbInitializer 文件，其中包含我的所有数据（即：我的数据库）。

using DrinkAndGo.Data.Models;\nusing Microsoft.AspNetCore.Builder;\nusing Microsoft.Extensions.DependencyInjection;\nusing System.Collections.Generic;\nusing System.Linq;\n\nnamespace DrinkAndGo.Data\n{\npublic class DbInitializer\n{\n    public static void Seed(IApplicationBuilder applicationBuilder)\n    {\n        AppDbContext context =\n            applicationBuilder.ApplicationServices.GetRequiredService<AppDbContext>();\n\n        if (!context.Categories.Any())\n        {\n            context.Categories.AddRange(Categories.Select(c => c.Value));\n        }\n\n        if (!context.Drinks.Any())\n        {\n            context.AddRange\n            (\n                new Drink\n                {\n                    Name = "Beer",\n                    Price = 7.95M,\n                    \n                    Category = Categories["Alcoholic"],\n                    ImageUrl = "http://imgh.us/beerL_2.jpg",\n                    InStock = true,\n                    IsPreferredDrink = true,\n                    ImageThumbnailUrl = "http://imgh.us/beerS_1.jpeg"\n                },\n                new Drink\n                {\n                    Name = "Rum & Coke",\n                    Price …

对于EF6,我可以通过以下方式检查数据库是否存在:

context.Database.Exists()

我怎么能在EF Core中这样做？

在.NET 5 Web应用程序中，我们在startup.cs中使用如下代码来使用实体框架初始化数据库：

using (var serviceScope = app.ApplicationServices.GetService<IServiceScopeFactory>().CreateScope())
{
    var context = serviceScope.ServiceProvider.GetRequiredService<ApplicationDbContext>();
    context.Database.EnsureCreated();
}

但在 .NET 6 中，我收到没有 ApplicationServices 的错误。我尝试了此处提出的解决方案，但随后出现运行时错误：“无法从根提供程序解析作用域服务‘WebApplication1.DataAccess.SchoolDbContext’”。我的program.cs中的完整代码如下：

using WebApplication1.DataAccess;
using Microsoft.EntityFrameworkCore;

WebApplicationBuilder builder = WebApplication.CreateBuilder(args);

builder.Configuration.AddJsonFile("appsettings.json");
builder.Services.AddRazorPages();

// Setup EF connection
// /sf/answers/3016870671/
// https://medium.com/executeautomation/asp-net-core-6-0-minimal-api-with-entity-framework-core-69d0c13ba9ab
builder.Services.AddDbContext<SchoolDbContext>(options => 
        options.UseSqlServer(builder.Configuration["Data:SchoolLocal:ConnectionString"]));

WebApplication app = builder.Build();

// /sf/answers/4988082851/
SchoolDbContext dbcontext = app.Services.GetRequiredService<SchoolDbContext>();
dbcontext.Database.EnsureCreated();
...

帮助会很棒。