我正在尝试为使用实体框架的CRUD操作创建基本的asp.net core web api，但出现以下错误：
InvalidOperationException: Unable to resolve service for type
'Corewebapi.Models.MyDatabaseContext' while attempting to activate 'Corewebapi.Controllers.LibrariesController'. and System.AggregateException:
'Some services are not able to be constructed (Error while validating the
service descriptor 'ServiceType: Corewebapi.Controllers.LibrariesController
Lifetime: Transient ImplementationType: Corewebapi.Controllers.LibrariesController': Unable to resolve service for type
'Corewebapi.Models.MyDatabaseContext' while attempting to activate 'Corewebapi.Controllers.LibrariesController'.)
我的代码是
using System;
using System.Collections.Generic;
namespace Corewebapi.Models
{
public partial class Library
{
public int Bookid { get; set; }
public string Bookname { get; set; }
public int? Price { get; set; }
public DateTime? Date { get; set; }
public string Author { get; set; }
}
}
用于数据库上下文
using System;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Metadata;
namespace Corewebapi.Models
{
public partial class MyDatabaseContext : DbContext
{
public MyDatabaseContext()
{
}
public MyDatabaseContext(DbContextOptions<MyDatabaseContext> options)
: base(options)
{
}
public virtual DbSet<Library> Library { get; set; }
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
if (!optionsBuilder.IsConfigured)
{
#warning To protect potentially sensitive information in your connection string, you should move it out of source code. See http://go.microsoft.com/fwlink/?LinkId=723263 for guidance on storing connection strings.
optionsBuilder.UseSqlServer("Server=localhost;Database=MyDatabase;Trusted_Connection=True;");
}
}
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Library>(entity =>
{
entity.HasKey(e => e.Bookid);
entity.Property(e => e.Bookid).HasColumnName("bookid");
entity.Property(e => e.Author)
.HasColumnName("author")
.HasMaxLength(50)
.IsUnicode(false);
entity.Property(e => e.Bookname)
.HasColumnName("bookname")
.HasMaxLength(50)
.IsUnicode(false);
entity.Property(e => e.Date)
.HasColumnName("date")
.HasColumnType("date");
entity.Property(e => e.Price).HasColumnName("price");
});
OnModelCreatingPartial(modelBuilder);
}
partial void OnModelCreatingPartial(ModelBuilder modelBuilder);
}
}
对于控制器
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using Corewebapi.Models;
namespace Corewebapi.Controllers
{
[Route("api/[controller]")]
[ApiController]
public class LibrariesController : ControllerBase
{
private readonly MyDatabaseContext _context;
public LibrariesController(MyDatabaseContext context)
{
_context = context;
}
// GET: api/Libraries
[HttpGet]
public async Task<ActionResult<IEnumerable<Library>>> GetLibrary()
{
return await _context.Library.ToListAsync();
}
// GET: api/Libraries/5
[HttpGet("{id}")]
public async Task<ActionResult<Library>> GetLibrary(int id)
{
var library = await _context.Library.FindAsync(id);
if (library == null)
{
return NotFound();
}
return library;
}
// PUT: api/Libraries/5
// To protect from overposting attacks, please enable the specific properties you want to bind to, for
// more details see https://aka.ms/RazorPagesCRUD.
[HttpPut("{id}")]
public async Task<IActionResult> PutLibrary(int id, Library library)
{
if (id != library.Bookid)
{
return BadRequest();
}
_context.Entry(library).State = EntityState.Modified;
try
{
await _context.SaveChangesAsync();
}
catch (DbUpdateConcurrencyException)
{
if (!LibraryExists(id))
{
return NotFound();
}
else
{
throw;
}
}
return NoContent();
}
// POST: api/Libraries
// To protect from overposting attacks, please enable the specific properties you want to bind to, for
// more details see https://aka.ms/RazorPagesCRUD.
[HttpPost]
public async Task<ActionResult<Library>> PostLibrary(Library library)
{
_context.Library.Add(library);
await _context.SaveChangesAsync();
return CreatedAtAction("GetLibrary", new { id = library.Bookid }, library);
}
// DELETE: api/Libraries/5
[HttpDelete("{id}")]
public async Task<ActionResult<Library>> DeleteLibrary(int id)
{
var library = await _context.Library.FindAsync(id);
if (library == null)
{
return NotFound();
}
_context.Library.Remove(library);
await _context.SaveChangesAsync();
return library;
}
private bool LibraryExists(int id)
{
return _context.Library.Any(e => e.Bookid == id);
}
}
}
staratup.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Corewebapi.Models;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
namespace Corewebapi
{
public class Startup
{
public Startup(IConfiguration configuration)
{
Configuration = configuration;
}
public IConfiguration Configuration { get; }
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
services.AddConnections();
// services.AddDbContext<MyDatabaseContext>(options =>
// options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));
services.AddMvc()
.AddControllersAsServices();
services.AddControllers().AddControllersAsServices();
}
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
app.UseHttpsRedirection();
app.UseRouting();
app.UseAuthorization();
app.UseEndpoints(endpoints =>
{
endpoints.MapControllers();
});
}
}
}
appsettings.json
{
"Logging": {
"LogLevel": {
"Default": "Information",
"Microsoft": "Warning",
"Microsoft.Hosting.Lifetime": "Information"
}
},
"AllowedHosts": "*"
}
答案 0 :(得分：0)
非常感谢那些试图帮助我的人，我通过在这些行中添加这些行来解决了
startup.cs
services.AddConnections();
services.AddDbContext<MyDatabaseContext>(options =>
options.UseSqlServer(@"Server=localhost;Database=MyDatabase;Trusted_Connection=True;"));
services.Configure<ConnectionString>(
Configuration.GetSection(nameof(ConnectionString)));
services.AddMvc()
.AddControllersAsServices();
services.AddControllers().AddControllersAsServices();