ASP.NET Core Web API：尝试激活时无法解析服务类型
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【中文标题】ASP.NET Core Web API：尝试激活时无法解析服务类型【英文标题】：ASP.NET Core Web API: Unable to resolve service for type while attempting to activate 【发布时间】：2021-09-23 19:05:25 【问题描述】：这是我第一次尝试 .NET API 并使用 .NET 核心。我曾经能够使用 ADO.NET 将数据库连接到项目，但显然不再支持，所以我使用 EF Core 使用这些包：microsoft.entityframeworkcore\5.0.8、microsoft.entityframeworkcore.sqlserver\5.0。 6，以及 microsoft.entityframeworkcore.tools\5.0.6。
然后我为数据库中的两个表生成了模型和数据库上下文，这似乎工作正常。但是，当我尝试访问 localhost/api/Statewides 时，我收到此错误：
System.InvalidOperationException: Unable to resolve service for type 'TestAPI.Models.RoadWay_HistoryContext' while attempting to activate 'TestAPI.Controllers.StatewidesController'.
at Microsoft.Extensions.DependencyInjection.ActivatorUtilities.GetService(IServiceProvider sp, Type type, Type requiredBy, Boolean isDefaultParameterRequired)
at lambda_method9(Closure , IServiceProvider , Object[] )
at Microsoft.AspNetCore.Mvc.Controllers.ControllerActivatorProvider.<>c__DisplayClass4_0.<CreateActivator>b__0(ControllerContext controllerContext)
at Microsoft.AspNetCore.Mvc.Controllers.ControllerFactoryProvider.<>c__DisplayClass5_0.<CreateControllerFactory>g__CreateController|0(ControllerContext controllerContext)
at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.InvokeInnerFilterAsync()
--- End of stack trace from previous location ---
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeFilterPipelineAsync>g__Awaited|19_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Logged|17_1(ResourceInvoker invoker)
at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
at Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIMiddleware.Invoke(HttpContext httpContext)
at Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.Invoke(HttpContext httpContext, ISwaggerProvider swaggerProvider)
at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)
HEADERS
=======
Accept: text/plain
Accept-Encoding: gzip, deflate, br
Accept-Language: en-US,en;q=0.9
Connection: close
Host: localhost:44324
Referer: https://localhost:44324/swagger/index.html
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.124 Safari/537.36
sec-ch-ua: " Not;A Brand";v="99", "Google Chrome";v="91", "Chromium";v="91"
sec-ch-ua-mobile: ?0
sec-fetch-site: same-origin
sec-fetch-mode: cors
sec-fetch-dest: empty
我真的不知道这意味着什么……我将提供数据库上下文和模型以及控制器和启动文件。如果您需要其他任何东西来回答这个问题，我很乐意提供。
全州控制器
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 TestAPI.Models;
namespace TestAPI.Controllers
[Route("api/[controller]")]
[ApiController]
public class StatewidesController : ControllerBase
private readonly RoadWay_HistoryContext _context;
public StatewidesController(RoadWay_HistoryContext context)
_context = context;
// GET: api/Statewides
[HttpGet]
public async Task<ActionResult<IEnumerable<Statewide>>> GetStatewides()
return await _context.Statewides.ToListAsync();
// GET: api/Statewides/5
[HttpGet("id")]
public async Task<ActionResult<Statewide>> GetStatewide(long id)
var statewide = await _context.Statewides.FindAsync(id);
if (statewide == null)
return NotFound();
return statewide;
// PUT: api/Statewides/5
// To protect from overposting attacks, see https://go.microsoft.com/fwlink/?linkid=2123754
[HttpPut("id")]
public async Task<IActionResult> PutStatewide(long id, Statewide statewide)
if (id != statewide.Id)
return BadRequest();
_context.Entry(statewide).State = EntityState.Modified;
try
await _context.SaveChangesAsync();
catch (DbUpdateConcurrencyException)
if (!StatewideExists(id))
return NotFound();
else
throw;
return NoContent();
// POST: api/Statewides
// To protect from overposting attacks, see https://go.microsoft.com/fwlink/?linkid=2123754
[HttpPost]
public async Task<ActionResult<Statewide>> PostStatewide(Statewide statewide)
_context.Statewides.Add(statewide);
await _context.SaveChangesAsync();
return CreatedAtAction("GetStatewide", new id = statewide.Id , statewide);
// DELETE: api/Statewides/5
[HttpDelete("id")]
public async Task<IActionResult> DeleteStatewide(long id)
var statewide = await _context.Statewides.FindAsync(id);
if (statewide == null)
return NotFound();
_context.Statewides.Remove(statewide);
await _context.SaveChangesAsync();
return NoContent();
private bool StatewideExists(long id)
return _context.Statewides.Any(e => e.Id == id);
Statewide.cs
using System;
using System.Collections.Generic;
#nullable disable
namespace TestAPI.Models
public partial class Statewide
public Statewide()
DocumentsNavigation = new HashSet<Document>();
public long Id get; set;
public string County get; set;
public string SignSys get; set;
public string RouteNoOrigImport get; set;
public int? RouteNo get; set;
public int? SuppDes get; set;
public string LocalName get; set;
public DateTime? DateNumber get; set;
public string Method get; set;
public string OriginalL get; set;
public string OriginalD get; set;
public string Projects get; set;
public string Documents get; set;
public string Comments get; set;
public int? District get; set;
public bool DuplicateOk get; set;
public string RightofWay get; set;
public bool ReservedRoute get; set;
public string ReservedBy get; set;
public DateTime? ReservedDate get; set;
public bool CpWorkCompleted get; set;
public string WorkComments get; set;
public string CpProjectNo get; set;
public int? ReservedCat get; set;
public string AddUser get; set;
public DateTime? DateAdded get; set;
public virtual ICollection<Document> DocumentsNavigation get; set;
数据库上下文
using System;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Metadata;
#nullable disable
namespace TestAPI.Models
public partial class RoadWay_HistoryContext : DbContext
public RoadWay_HistoryContext()
public RoadWay_HistoryContext(DbContextOptions<RoadWay_HistoryContext> options)
: base(options)
public virtual DbSet<Document> Documents get; set;
public virtual DbSet<Statewide> Statewides 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. You can avoid scaffolding the connection string by using the Name= syntax to read it from configuration - see https://go.microsoft.com/fwlink/?linkid=2131148. For more guidance on storing connection strings, see http://go.microsoft.com/fwlink/?LinkId=723263.
optionsBuilder.UseSqlServer("Server=dotb6gisdbst01;Database=RoadWay_History;Trusted_Connection=True;");
protected override void OnModelCreating(ModelBuilder modelBuilder)
modelBuilder.HasAnnotation("Relational:Collation", "SQL_Latin1_General_CP1_CI_AS");
modelBuilder.Entity<Document>(entity =>
entity.Property(e => e.Id).HasColumnName("ID");
entity.Property(e => e.AddUser)
.HasMaxLength(25)
.HasColumnName("Add_User");
entity.Property(e => e.DateAdded)
.HasColumnType("date")
.HasColumnName("Date_Added");
entity.Property(e => e.DocLocation)
.HasMaxLength(255)
.HasColumnName("Doc_Location");
entity.Property(e => e.DocType)
.HasMaxLength(255)
.HasColumnName("Doc_Type");
entity.Property(e => e.FileContents)
.HasMaxLength(255)
.HasColumnName("File_Contents");
entity.Property(e => e.OrderDate)
.HasColumnType("date")
.HasColumnName("Order_Date");
entity.Property(e => e.StatewideId).HasColumnName("Statewide_ID");
entity.HasOne(d => d.Statewide)
.WithMany(p => p.DocumentsNavigation)
.HasForeignKey(d => d.StatewideId)
.HasConstraintName("FK_Documents_Statewide");
);
modelBuilder.Entity<Statewide>(entity =>
entity.ToTable("Statewide");
entity.Property(e => e.Id).HasColumnName("ID");
entity.Property(e => e.AddUser)
.HasMaxLength(25)
.HasColumnName("Add_User");
entity.Property(e => e.County)
.HasMaxLength(255)
.HasColumnName("COUNTY");
entity.Property(e => e.CpProjectNo)
.HasMaxLength(255)
.HasColumnName("CP_ProjectNo");
entity.Property(e => e.CpWorkCompleted).HasColumnName("CP_WorkCompleted");
entity.Property(e => e.DateAdded)
.HasColumnType("date")
.HasColumnName("Date_Added");
entity.Property(e => e.DateNumber).HasColumnType("date");
entity.Property(e => e.DuplicateOk).HasColumnName("Duplicate OK");
entity.Property(e => e.LocalName).HasMaxLength(255);
entity.Property(e => e.Method).HasMaxLength(255);
entity.Property(e => e.OriginalD).HasMaxLength(255);
entity.Property(e => e.OriginalL).HasMaxLength(255);
entity.Property(e => e.ReservedDate).HasColumnType("date");
entity.Property(e => e.RightofWay).HasMaxLength(255);
entity.Property(e => e.RouteNoOrigImport).HasMaxLength(255);
entity.Property(e => e.SignSys).HasMaxLength(255);
entity.Property(e => e.WorkComments)
.HasMaxLength(255)
.HasColumnName("Work_Comments");
);
OnModelCreatingPartial(modelBuilder);
partial void OnModelCreatingPartial(ModelBuilder modelBuilder);
Startup.cs
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Microsoft.OpenApi.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
namespace TestAPI
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.AddControllers();
services.AddSwaggerGen(c =>
c.SwaggerDoc("v1", new OpenApiInfo Title = "TestAPI", Version = "v1" );
);
// 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.UseSwagger();
app.UseSwaggerUI(c => c.SwaggerEndpoint("/swagger/v1/swagger.json", "TestAPI v1"));
app.UseHttpsRedirection();
app.UseRouting();
app.UseAuthorization();
app.UseEndpoints(endpoints =>
endpoints.MapControllers();
);
【问题讨论】：
【参考方案1】：您收到此错误是因为您尚未将RoadWay_HistoryContext 注册到服务容器。通过依赖注入使用的所有服务都必须注册。这就是类在您尝试使用它们时能够解析服务的方式。这就是您通过将此行添加到 ConfigureServices 方法来修复它的方法。
services.AddDbContext<RoadWay_HistoryContext>(opts => opts.UseSqlServer(Configuration.GetConnectionString("ConnectionName")));
更新
"Logging":
"LogLevel":
"Default": "Information",
"Microsoft": "Warning",
"Microsoft.Hosting.Lifetime": "Information"
,
"ConnectionStrings":
"ConnectionName": "Server=ServerOfDatabase;Database=DatabaseName;Trusted_Connection=True;MultipleActiveResultSets=true"
【讨论】：
非常感谢您。 2 个问题：在哪里可以找到“我的连接名称”？我认为 RoadWay_HistoryContext 是这个名字......第二，你能不能给我指出一个好的文档？我找不到正确的文档来解决这个问题以挽救我的生命。 @GrillOwner69420 理想情况下，您应该将它放在 appsettings.development.json 中。我会更新答案以反映这一点。 在 appsettings.development.json 中放置什么？连接名称？我想我可以做到，但我必须先找到我的连接名称。我的连接名称是什么，如何找到它？就像我说的，我认为 RoadWay_HistoryContext 是连接名称。我不知道连接名称是什么。我不记得曾经被要求或声明过“连接名称” 连接名称可以是任何名称。它只是一个变量，其值为您的数据库连接字符串 我发现这是一个愚蠢的错误。非常感谢您的帮助！以上是关于ASP.NET Core Web API：尝试激活时无法解析服务类型的主要内容，如果未能解决你的问题，请参考以下文章
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