如何使用DB上下文正确实现存储库模式。NET

Question

我正在创建.NET Core 6控制台应用程序。

我有一个存储库类StorageCompetitorRepository实现接口istoragecompetitorrepository。

以下是program.cs在我尝试初始化时的null：

  _storageCompetitorRepository = serviceProvider.GetService<StorageCompetitorRepository>();

storagecompetitorrepository类通过构造器初始化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");
    }
}

为什么我对将其作为null添加为瞬态服务的repo类的初始化？

任何想法或建议将不胜感激。

Answer 1

您正在注册接口，但要求进行具体的实现。

在这里，您是在说：“解决一个IstorageCompetitorRepository时，请给我StorageCompetitorRepository。

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

稍后，您试图解决存储库的具体实现，而DI找不到它，因为它仅在容器中注册为界面作为界面，是使其作为界面，使其成为界面感觉？
更改此信息：

_storageCompetitorRepository = serviceProvider.GetService<StorageCompetitorRepository>();

对此：

_storageCompetitorRepository = serviceProvider.GetService<IStorageCompetitorRepository>();

如果您想能够解决具体实现，则需要注册它。

AddTransient<StorageCompetitorRepository>();

然后，如果您也希望也能够通过接口解析，也可以将其注册为这样的接口。

AddTransient<IStorageCompetitorRepository, StorageCompetitorRepository>();

或者

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