An error occurred while starting the application. InvalidOperationException: Scheme already exists: Identity.Application

Question

An error occurred while starting the application.
InvalidOperationException: Scheme already exists: Identity.Application Microsoft.AspNetCore.Authentication.AuthenticationOptions.AddScheme(string name, Action configureBuilder)

I am working on ASP.NET Core WEB API with Angular template in VS 2017. I am having following code in the ConfigureServices() method of the Statrtup.cs class

public void ConfigureServices(IServiceCollection services)
{
    services.AddDbContext<AuthDbContext>(options =>
    {
        options.UseSqlServer(Configuration.GetConnectionString("AuthDbContextConnection"));
    });

    services.AddDbContext<AppNgDbContext>(options =>
    {
        options.UseSqlServer(Configuration.GetConnectionString("AppNgDbContextConnection"));
    });

    services.AddTransient<SecurityService>();

    services.AddIdentity<IdentityUser, IdentityRole>()
            .AddEntityFrameworkStores<AuthDbContext>()
            .AddDefaultTokenProviders();

    services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
            .AddJwtBearer(options =>
            {
                // 1. Load the JST Secret Key to Verify and Validate Token
                // read key from appsettings.json
                var secretKey = Convert.FromBase64String(Configuration["JWTAppSettings:SecretKey"]);
                // 2. Defining the Mechanism for Validating Received Token from Client
                options.TokenValidationParameters = new TokenValidationParameters
                {
                    ValidateIssuer = false,
                    ValidateAudience = false,
                    ValidateIssuerSigningKey = true,
                    IssuerSigningKey = new SymmetricSecurityKey(secretKey)
                };
            });

    services.AddScoped<IRepository<Orders, int>, OrdersRepository>();

    services.AddMvc()
            .AddJsonOptions(options => options.SerializerSettings.ContractResolver = new DefaultContractResolver())
            .SetCompatibilityVersion(CompatibilityVersion.Version_2_2);

    // In production, the Angular files will be served from this directory
    services.AddSpaStaticFiles(configuration =>
    {
        configuration.RootPath = "ClientApp/dist";
    });
}

When I run the application, it should load so that I can access the WEB API but unfortunately it produces the following error

An error occurred while starting the application.
InvalidOperationException: Scheme already exists: Identity.Application Microsoft.AspNetCore.Authentication.AuthenticationOptions.AddScheme(string name, Action configureBuilder)
InvalidOperationException: Scheme already exists: Identity.Application Microsoft.AspNetCore.Authentication.AuthenticationOptions.AddScheme(string name, Action configureBuilder) Microsoft.AspNetCore.Authentication.AuthenticationBuilder+<>c__DisplayClass4_0.b__0(AuthenticationOptions o) Microsoft.Extensions.Options.ConfigureNamedOptions.Configure(string name, TOptions options) Microsoft.Extensions.Options.OptionsFactory.Create(string name) Microsoft.Extensions.Options.OptionsManager+<>c__DisplayClass5_0.b__0() System.Lazy.ViaFactory(LazyThreadSafetyMode mode) System.Lazy.ExecutionAndPublication(LazyHelper executionAndPublication, bool useDefaultConstructor) System.Lazy.CreateValue() Microsoft.Extensions.Options.OptionsCache.GetOrAdd(string name, Func createOptions) Microsoft.Extensions.Options.OptionsManager.Get(string name) Microsoft.Extensions.Options.OptionsManager.get_Value() Microsoft.AspNetCore.Authentication.AuthenticationSchemeProvider..ctor(IOptions options, IDictionary schemes) Microsoft.AspNetCore.Authentication.AuthenticationSchemeProvider..ctor(IOptions options) Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, ServiceProviderEngineScope scope) Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor.VisitCallSite(IServiceCallSite callSite, TArgument argument) Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScoped(ScopedCallSite scopedCallSite, ServiceProviderEngineScope scope) Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitSingleton(SingletonCallSite singletonCallSite, ServiceProviderEngineScope scope) Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor.VisitCallSite(IServiceCallSite callSite, TArgument argument) Microsoft.Extensions.DependencyInjection.ServiceLookup.DynamicServiceProviderEngine+<>c__DisplayClass1_0.b__0(ServiceProviderEngineScope scope) Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngine.GetService(Type serviceType, ServiceProviderEngineScope serviceProviderEngineScope) Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngine.GetService(Type serviceType) Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService(Type serviceType) Microsoft.Extensions.Internal.ActivatorUtilities+ConstructorMatcher.CreateInstance(IServiceProvider provider) Microsoft.Extensions.Internal.ActivatorUtilities.CreateInstance(IServiceProvider provider, Type instanceType, object[] parameters) Microsoft.AspNetCore.Builder.UseMiddlewareExtensions+<>c__DisplayClass4_0.b__0(RequestDelegate next) Microsoft.AspNetCore.Builder.Internal.ApplicationBuilder.Build() Microsoft.AspNetCore.Hosting.Internal.WebHost.BuildApplication()

Answer 1

I had a similar issue. This might be more helpful for people using .Net Core 3.0. After digging around I found out that once you create an "Identity" area using scaffolding. A file called "IdentityHostingStartup.cs" is created inside the Identity folder.

Inside the class, another instance of "AddDefaultIdentity" is created along with a few other services.

If you remove the "addDefaultIdentity" from your "Startup.cs" your app should start. Also, If you are getting a null connection string error. Update the connection string inside of the IdentityHostintgStartup.cs

Note: Deleting either of the addDefaultIdentities will work. You just can't have it in both locations.

Hope this helps.

Answer 2

After doing some tries I found the following lines worked for me

  services.AddIdentityCore<IdentityUser>().AddRoles<IdentityRole>()
            .AddEntityFrameworkStores<AuthDbContext>()
            .AddDefaultTokenProviders();

I Added this instead of the following code

services.AddIdentity<IdentityUser, IdentityRole>()

.AddEntityFrameworkStores() .AddDefaultTokenProviders();

This works for me after just utilizing complete 5-6 hours.

Thanks Mahesh Sabnis