Bootstrap
本文主要介绍ASP.NET Core中,在Startup.cs中ConfigureServices()方法中调用services.AddMvc()方法,出现异常(KeyNotFoundException: The given key was not present in the dictionary. )的解决方法。

1、项目中调用代码

public IServiceProvider ConfigureServices(IServiceCollection services)
{
   // Add services to the collection.
   services.AddMvc();
}

抛出异常信息

KeyNotFoundException: The given key was not present in the dictionary. System.Collections.Generic.Dictionary.get_Item(TKey key) 
Microsoft.AspNetCore.Mvc.Internal.DefaultAssemblyPartDiscoveryProvider+CandidateResolver.ComputeClassification(string dependency) 
Microsoft.AspNetCore.Mvc.Internal.DefaultAssemblyPartDiscoveryProvider+CandidateResolver.ComputeClassification(string dependency) 
Microsoft.AspNetCore.Mvc.Internal.DefaultAssemblyPartDiscoveryProvider+CandidateResolver.ComputeClassification(string dependency) 
Microsoft.AspNetCore.Mvc.Internal.DefaultAssemblyPartDiscoveryProvider+CandidateResolver.ComputeClassification(string dependency) 
Microsoft.AspNetCore.Mvc.Internal.DefaultAssemblyPartDiscoveryProvider+CandidateResolver+d__4.MoveNext() System.Linq.Enumerable+d__17.MoveNext() System.Linq.Enumerable+WhereSelectEnumerableIterator.MoveNext() Microsoft.Extensions.DependencyInjection.MvcCoreServiceCollectionExtensions.GetApplicationPartManager(IServiceCollection services) 
Microsoft.Extensions.DependencyInjection.MvcCoreServiceCollectionExtensions.AddMvcCore(IServiceCollection services) 
Microsoft.Extensions.DependencyInjection.MvcServiceCollectionExtensions.AddMvc(IServiceCollection services) MyWebApiProject.Startup.ConfigureServices(IServiceCollection services) in Startup.cs System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() 
Microsoft.AspNetCore.Hosting.ConventionBasedStartup.ConfigureServices(IServiceCollection services) Microsoft.AspNetCore.Hosting.Internal.WebHost.EnsureApplicationServices() Microsoft.AspNetCore.Hosting.Internal.WebHost.BuildApplication()

csproj文件内容

<TargetFramework>net461</TargetFramework>
<ItemGroup>
<PackageReference Include="Autofac" Version="4.6.2" />
<PackageReference Include="Autofac.Extensions.DependencyInjection" Version="4.1.0" />
<PackageReference Include="EntityFramework" Version="6.2.0" />
<PackageReference Include="Microsoft.ApplicationInsights.AspNetCore" Version="2.0.1" />
<PackageReference Include="Microsoft.AspNetCore" Version="1.1.2" />
<PackageReference Include="Microsoft.AspNetCore.Authentication.JwtBearer" Version="1.1.2" />
<PackageReference Include="Microsoft.AspNetCore.Mvc" Version="1.1.3" />
<PackageReference Include="Microsoft.AspNetCore.SignalR.Server" Version="0.2.0-preview2-22683" />
<PackageReference Include="Microsoft.AspNetCore.WebSockets" Version="1.0.2" />
<PackageReference Include="Microsoft.Extensions.Logging.Debug" Version="1.1.2" />
<PackageReference Include="Microsoft.IdentityModel.Tokens" Version="5.1.5" />
<PackageReference Include="Microsoft.VisualStudio.SlowCheetah" Version="3.0.61" />
<PackageReference Include="NLog.Web.AspNetCore" Version="4.4.1" />
<PackageReference Include="Swashbuckle.AspNetCore" Version="1.0.0" />
<PackageReference Include="System.IdentityModel.Tokens.Jwt" Version="5.1.5" />
<PackageReference Include="System.Net.Http" Version="4.3.3" />

2、解决方法

在添加MVC之前添加ApplicationPartManager

var manager = new ApplicationPartManager();
manager.ApplicationParts.Add(new AssemblyPart(typeof(Startup).Assembly));
services.AddSingleton(manager);
services.AddMvc();

参考文档https://github.com/aspnet/Home/issues/3132