使用 DI 实现 Repository 和 Db Context .Net Core Console Entity Framework

Question

我正在创建 .NET Core 6 控制台应用程序。

我有一个实现接口 IStorageCompetitorRepository.

的存储库 class StorageCompetitorRepository

当我尝试初始化时，以下内容在 Program.cs 中中断并显示为 null：

  _storageCompetitorRepository = serviceProvider.GetService<StorageCompetitorRepository>();

StorageCompetitorRepositoryclass通过构造函数初始化DbContext

Program.cs:

using Microsoft.Extensions.DependencyInjection;

class Program
{
     private static StorageCompetitorRepository _storageCompetitorRepository;
    
     static void Main(string[] args)
     {
         // configure services 
         var services = new ServiceCollection()
                    .AddTransient<IStorageCompetitorRepository, StorageCompetitorRepository>();
    
         // create service provider 
         var serviceProvider = services.BuildServiceProvider();
         _storageCompetitorRepository = serviceProvider.GetService<StorageCompetitorRepository>();
    
         bool runLoaderTool = true;

         while (runLoaderTool)
         {
             runLoaderTool = ChooseElasticIndexMenu(runLoaderTool, _storageCompetitorRepository);
         }
     }

     public static bool ChooseElasticIndexMenu(bool runLoaderTool, StorageCompetitorRepository storageCompetitorRepository)
     {
         // didn't add the full code that returns the boolean all you need
         // to know that the repo class method is called here 
         storageCompetitorRepository.GetStorageCompetitors();
     }
}

StorageCompetitorRepository:

public class StorageCompetitorRepository : IStorageCompetitorRepository
{
    string DatabaseServer = ConfigurationManager.AppSettings["DataBaseServer"];
    private readonly DevModelContext _devModelContext;
    public StorageCompetitorRepository(DevModelContext devModelContext) => _devModelContext = devModelContext;

    public List<storage_competitor> GetStorageCompetitors()
    {
        try
        {
            var ctx = _devModelContext.StorageCompetitors;
            var storageCompetitorList = (from sc in ctx
                                         where sc.active == true && sc.id_period == (from s in ctx select s).Max(s => s.id_period)
                                         select sc).Distinct()
                                         .OrderBy(sc => sc).ToList();
            var countStorageCompetitors = storageCompetitorList.Count();
            Console.WriteLine($"{countStorageCompetitors} Storage Competitors were found in SQL Server : {DatabaseServer} Database : Competitors");
 
            return storageCompetitorList; 
        }
        catch
        {
            return new List<storage_competitor>();
        }
    }
}

DevModelContext:

public class DevModelContext : DbContext
{
    string connectionString = ConfigurationManager.ConnectionStrings["connCompetitorsDev"].ConnectionString;

    public DevModelContext(DbContextOptions<DevModelContext> options) : base(options)
    {
    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer(connectionString);
    }

    public DbSet<storage_competitor> StorageCompetitors { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<storage_competitor>().ToTable("storage_competitor");
    }
}

为什么我对 repo class 的初始化在将其添加为临时服务时显示为 null？

如有任何想法或建议，我们将不胜感激。

Answer 1

您注册的是接口，要求具体实现

你说的是“解析 IStorageCompetitorRepository 时，给我 StorageCompetitorRepository”

var services = new ServiceCollection()
                .AddTransient<IStorageCompetitorRepository, StorageCompetitorRepository>();

后来你想解决repository的具体实现，DI找不到，因为它只是作为接口注册到容器中，有意义吗？改变这个：

_storageCompetitorRepository = serviceProvider.GetService<StorageCompetitorRepository>();

为此：

_storageCompetitorRepository = serviceProvider.GetService<IStorageCompetitorRepository>();

如果你想能够解决具体的实现，你需要注册它。

AddTransient<StorageCompetitorRepository>();

如果你也想通过接口解析它，你也可以像这样将它注册为接口。

AddTransient<IStorageCompetitorRepository, StorageCompetitorRepository>();

或

AddTransient<IStorageCompetitorRepository>(x => x.GetRequiredService<StorageCompetitorRepository);

使用 DI 实现 Repository 和 Db Context .Net Core Console Entity Framework

Implement Repository and Db Context .Net Core Console Entity Framework with DI

c#

dependency-injection

console-application

entity-framework-core

.net-core