主页 / coding / 问题 / 77068302
Accepted
Mehmet
Asked: 2023-09-08 23:50:39 +0800 CST

ASP .NET 无法解析类型的服务

  • 772

我正在跟随一个Instructor，一开始一切都很顺利，但是当我将项目发布到github后，项目的文件发生了变化，我认为我做错了什么，后来我编辑了内容。但有一点我错过了，我认为我无法建立数据库连接（或者我误解了它）我也尝试了有关此主题的页面上的解决方案，但它不起作用。请你帮助我好吗？

我得到的错误如下

System.AggregateException: 'Some services are not able to be constructed (Error while validating the service descriptor 'ServiceType: Repositories.RepositoryContext Lifetime: Scoped ImplementationType: Repositories.RepositoryContext': Unable to resolve service for type 'Microsoft.EntityFrameworkCore.DbSet1[Entities.Models.Product]' 尝试激活 'Repositories.RepositoryContext' 时。）（验证服务描述符 'ServiceType: Repositories.Contracts.IRepositoryManager Lifetime: Scoped ImplementType: Repositories.RepositoryManager' 时出错：无法解析服务1[Entities.Models.Product]' while attempting to activate 'Repositories.RepositoryContext'.) (Error while validating the service descriptor 'ServiceType: Repositories.Contracts.IProductRepository Lifetime: Scoped ImplementationType: Repositories.ProductRepository': Unable to resolve service for type 'Microsoft.EntityFrameworkCore.DbSet尝试激活“Repositories.RepositoryContext”时键入“Microsoft.EntityFrameworkCore.DbSet 1[Entities.Models.Product]”。）

InvalidOperationException: Unable to resolve service for type 'Microsoft.EntityFrameworkCore.DbSet1[Entities.Models.Product]'，同时尝试激活“Repositories.RepositoryContext”。`

我一一检查了我的存储库层，一一检查了我的 Program.cs 链接，我检查了微软网站上的说明，但我想我无法以我目前的知识水平解决这个问题。

我的存储库上下文页面如下所示

public class RepositoryContext : DbContext
{
    public DbSet<Product> Products { get; set; } 
    public DbSet<Category> Categories { get; set; } 


    public RepositoryContext(DbContextOptions<RepositoryContext> options, DbSet<Product> products, DbSet<Category> categories) :
        base(options) 
    {
       
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder); 
        modelBuilder.Entity<Product>()
            .HasData(new Product() { Id = 1, ProductName = "Laptop", Price = 1000 },
                new Product() { Id = 2, ProductName = "Keyboard", Price = 500 },
                new Product() { Id = 3, ProductName = "Computer", Price = 2500 },
                new Product() { Id = 4, ProductName = "Monitor", Price = 1000 },
                new Product() { Id = 5, ProductName = "Deck", Price = 500 }
            ); 
        modelBuilder.Entity<Category>()
            .HasData(
                new Category() { CategoryId = 1, CategoryName = "Book" },
                new Category() { CategoryId = 2, CategoryName = "Electronic" });
    }
}

这是我在程序开头的代码

var builder = WebApplication.CreateBuilder(args);
builder.Services
    .AddControllersWithViews(); 
builder.Services.AddDbContext<RepositoryContext>(options =>
{
    options.UseSqlite(builder.Configuration.GetConnectionString
        ("sqlconnection"), 
        b => b.MigrationsAssembly("StoreApp")); 
});
builder.Services.AddScoped<IRepositoryManager, RepositoryManager>();
builder.Services.AddScoped<IProductRepository, ProductRepository>();


var app = builder.Build();

app.UseStaticFiles(); 
app.UseHttpsRedirection(); 
app.UseRouting(); 


app.MapControllerRoute(
    name: "default",
    pattern: "{controller=Home}/{action=Index}/{id?}"); 

app.Run();

物体有这个形状

public class Product
{
    public int Id { get; set; }
    public String? ProductName { get; set; } = String.Empty; 
    public decimal Price { get; set; }
}


    public class Category
    {
        public int CategoryId { get; set; }
        public String? CategoryName { get; set; }= String.Empty;
        
    }
c#

2 个回答

  1. Best Answer

    你不应该注入DbSet's，只需将它们从 ctor 中删除：

    public class RepositoryContext : DbContext
{
    public DbSet<Product> Products { get; set; } 
    public DbSet<Category> Categories { get; set; } 


    public RepositoryContext(DbContextOptions<RepositoryContext> options) :
        base(options) 
    {
       
    }
    ...
}

    或者：

    public class RepositoryContext : DbContext
{
    public DbSet<Product> Products => Set<Product>();
    public DbSet<Category> Categories => Set<Category>();


    public RepositoryContext(DbContextOptions<RepositoryContext> options) :
        base(options) 
    {
       
    }
    ...
}

    处理可空性警告（如果有）。

    也可以看看：

    • 2

  2. 您需要将什么注入DbSet<Product>构造DbSet<Category>函数中？如果构造函数中没有这些参数，应该可以正常工作。

    这两个参数无法构造，这就是导致服务解析异常的原因。

    • 1

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