找到了多个名为 'NewProject.Models.DbContext' 的 DbContext 通过使用精确大小写的完全限定名称指定要使用的一个

Question

我正在使用 Asp.Net Core 2.1 开发 Web 应用程序。在我使用脚手架添加新身份后，它为我生成了这些代码：

代码生成于IdentityStartup.cs

[assembly:HostingStartup(typeof(ShareAndCare.Areas.Identity.IdentityHostingStartup))]
namespace ShareAndCare.Areas.Identity
{
    public class IdentityHostingStartup : IHostingStartup
    {
        public void Configure(IWebHostBuilder builder)
        {
            builder.ConfigureServices((context, services) => {

                services.AddDbContext<ShareAndCareContext>(options =>
                   options.UseLazyLoadingProxies().UseSqlServer(
                       context.Configuration.GetConnectionString("ShareAndCareContextConnection")));

                services.AddIdentity<ShareAndCareUser, IdentityRole>()
                .AddEntityFrameworkStores<ShareAndCareContext>()
                .AddDefaultTokenProviders();

                services.AddSingleton<IEmailSender, EmailSender>();               

            });

        }
    }
}

代码生成于Startup.cs

    namespace ShareAndCare
    {
        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.Configure<CookiePolicyOptions>(options =>
                {
                    // This lambda determines whether user consent for non-essential cookies is needed for a given request.
                    options.CheckConsentNeeded = context => true;
                    options.MinimumSameSitePolicy = SameSiteMode.None;
                });            

                services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);            
            }    
            // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
            public void Configure(IApplicationBuilder app, IHostingEnvironment env, IServiceProvider serviceProvider)
            {
                if (env.IsDevelopment())
                {
                    app.UseDeveloperExceptionPage();
                }
                else
                {
                    app.UseExceptionHandler("/Home/Error");
                    app.UseHsts();
                }

                app.UseHttpsRedirection();
                app.UseStaticFiles();
                app.UseAuthentication();
                app.UseCookiePolicy();

                app.UseMvc(routes =>
                {
                    routes.MapRoute(
                        name: "default",
                        template: "{controller=Home}/{action=Index}/{id?}");
                });                
            }   
        }
    }

在我想使用 EF 搭建一个带有控制器和视图的模型之前，它一直运行良好。设置所有内容并单击“确定”时，我收到一条错误消息：找到多个名为 'ShareAndCare.Models.ShareAndCareContext' 的 DbContext。通过使用确切大小写的完全限定名称来指定要使用的名称。 我检查了所有文件夹和名称空间，但那里没有问题，只有一个上下文具有该名称。那么问题出在哪里？

Answer 1

我把问题和答案留在这里，这样人们就不会像我一样疯狂地手动寻找所有可能的解决方案。我发现在 IdentityHostingStartup.cs 的 Configure 方法中添加上下文导致了问题。我更改了将上下文添加到 Startup.cs 的 Configure 方法的位置，它工作得很好。

namespace ShareAndCare
{
    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.Configure<CookiePolicyOptions>(options =>
            {
                // This lambda determines whether user consent for non-essential cookies is needed for a given request.
                options.CheckConsentNeeded = context => true;
                options.MinimumSameSitePolicy = SameSiteMode.None;
            });            

            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);

            services.AddDbContext<ShareAndCareContext>(options =>
                   options.UseLazyLoadingProxies().UseSqlServer(
                       Configuration.GetConnectionString("ShareAndCareContextConnection")));

        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env, IServiceProvider serviceProvider)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Home/Error");
                app.UseHsts();
            }

            app.UseHttpsRedirection();
            app.UseStaticFiles();
            app.UseAuthentication();
            app.UseCookiePolicy();

            app.UseMvc(routes =>
            {
                routes.MapRoute(
                    name: "default",
                    template: "{controller=Home}/{action=Index}/{id?}");
            });                
        }   
    }
}

Answer 2

我刚刚删除了 2 个文件：

Areas/Identity/Data/APNameIdentityDbContext.cs 和
Areas/Identity/IdentityHostingStartup.cs

这修正了错误！

Answer 3

在我的案例中，我添加了 services.AddDbContext<DBContext> 但我的 DBContext 名称是

ApplicationDBContext.

在 Startup.cs 中更改了我的名字并且成功了

 public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllers();
            services.AddDbContext<ApplicationDBContext>(options => options.UseSqlServer(Configuration["Data:ConnectionStrings:DefaultConnection"]));
        }

希望这对某人有所帮助:)

找到了多个名为 'NewProject.Models.DbContext' 的 DbContext 通过使用精确大小写的完全限定名称指定要使用的一个

More than one DbContext named 'NewProject.Models.DbContext' was found Specify which one to use by providing its fully qualified name using exact case

c#

entity-framework

asp.net-mvc-scaffolding

asp.net-core

asp.net-core-2.1