do.net 意外退出 - 在 ASP.NET Core 中创建新项目后

Question

I'm getting this warning while creating new MVC project using ASP.NET Core (both 3.1 version and 5.0 version):

do.net quit unexpectedly

Because the warning description does show me where the problem comes from, so I don't know where to start.

This is my Startup.cs file:

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)
    {
        
    }

    // 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.UseMigrationsEndPoint();
        }
        else
        {
            app.UseExceptionHandler("/Home/Error");
            // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
            app.UseHsts();
        }
        app.UseHttpsRedirection();
        app.UseStaticFiles();

        app.UseRouting();

        app.UseAuthentication();
        app.UseAuthorization();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllerRoute(
                name: "default",
                pattern: "{controller=Home}/{action=Index}/{id?}");
            endpoints.MapRazorPages();
        });
    }
}

Am I missing something?

Answer 1

There are multiple cases to get this warning. Some problem can be fixed inside the method ConfigureServices in the file Startup.cs .

If you are using Visual Studio, you can open Application Output tab (View -> Other Windows -> Application Output) .

If you've got some message, such as:

Case 1:

Unhandled exception. System.InvalidOperationException: Unable to find the required services. Please add all the required services by calling 'IServiceCollection.AddAuthorization' inside the call to 'ConfigureServices(...)' in the application startup code.

Fixed: Calling services.AddAuthorization(); method inside the ConfigureServices method.

Note: It's different from services.AddAuthentication(); (this service can be used when you want to enable some services like: Login with Facebook/Google/Twitter...) .

---

Case 2:

Unhandled exception. System.InvalidOperationException: Unable to find the required services. Please add all the required services by calling 'IServiceCollection.AddControllers' inside the call to 'ConfigureServices(...)' in the application startup code.

Fixed: Calling services.AddControllersWithViews(); or services.AddControllers(); service inside that method to solve the problem.

---

Case 3:

Unhandled exception. System.InvalidOperationException: Unable to find the required services. Please add all the required services by calling 'IServiceCollection.AddRazorPages' inside the call to 'ConfigureServices(...)' in the application startup code.

This error ocurrs when you enable to use Razor Pages . To solve this problem, you need to add services.AddRazorPages(); service.

---

Case 4:

An unhandled exception has occurred while executing the request.

System.InvalidOperationException: No service for type 'Microsoft.AspNetCore.Identity.UserManager`1[Microsoft.AspNetCore.Identity.IdentityUser]' has been registered.

You've got this error when missing to add identity service. This can be done by one of these ways:

services.AddDefaultIdentity<IdentityUser>(options =>
{
    //options.Password.RequireDigit = false;
    //options.Password.RequiredLength = 8;
    //options.Password.RequireLowercase = false;
    //options.Password.RequireNonAlphanumeric = false;
    //options.Password.RequireUppercase = false;
}).AddEntityFrameworkStores<ApplicationDbContext>();

or

services.AddIdentity<IdentityUser, IdentityRole>(options =>
{
    //options.Password.RequireDigit = false;
    //options.Password.RequiredLength = 8;
    //options.Password.RequireLowercase = false;
    //options.Password.RequireNonAlphanumeric = false;
    //options.Password.RequireUppercase = false;
}).AddEntityFrameworkStores<ApplicationDbContext>();

If you want to extend IdentityUser class to add more property like LastSignedIn :

public class User : IdentityUser
{
    public DateTimeOffset LastSignedIn { get; set; }
}

you can replace IdentityUser with User when adding identity service:

services.AddIdentity<User, IdentityRole>(options => {})
        .AddEntityFrameworkStores<ApplicationDbContext>();

---

Case 5:

Unhandled exception. System.AggregateException: Some services are not able to be constructed (Error while validating the service descriptor 'ServiceType: Microsoft.AspNetCore.Identity.IUserClaimsPrincipalFactory 1[Microsoft.AspNetCore.Identity.IdentityUser] Lifetime: Scoped ImplementationType: Microsoft.AspNetCore.Identity.UserClaimsPrincipalFactory 1[Microsoft.AspNetCore.Identity.IdentityUser]': Unable to resolve service for type 'X.Data.ApplicationDbContext' while attempting to activate 'Microsoft.AspNetCore.Identity.EntityFrameworkCore.UserOnlyStore 6[Microsoft.AspNetCore.Identity.IdentityUser,X.Data.ApplicationDbContext,System.String,Microsoft.AspNetCore.Identity.IdentityUserClaim 1[System.String],Microsoft.AspNetCore.Identity.IdentityUserLogin 1[System.String],Microsoft.AspNetCore.Identity.IdentityUserToken 1[System.String]]'.) (Error while validating the service descriptor 'ServiceType: Microsoft.AspNetCore.Identity.UserManager 1[Microsoft.AspNetCore.Identity.IdentityUser] Lifetime: Scoped ImplementationType: Microsoft.AspNetCore.Identity.UserManager 1[Microsoft.AspNetCore.Identity.IdentityUser] Lifetime: Scoped ImplementationType: Microsoft.AspNetCore.Identity.UserManager 1[Microsoft.AspNetCore.Identity.IdentityUser]': Unable to resolve service for type 'X.Data.ApplicationDbContext' while attempting to activate 'Microsoft.AspNetCore.Identity.EntityFrameworkCore.UserOnlyStore 6[Microsoft.AspNetCore.Identity.IdentityUser,X.Data.ApplicationDbContext,System.String,Microsoft.AspNetCore.Identity.IdentityUserClaim 1[System.String],Microsoft.AspNetCore.Identity.IdentityUserLogin 1[System.String],Microsoft.AspNetCore.Identity.IdentityUserToken 1[System.String]]'.) (Error while validating the service descriptor 'ServiceType: Microsoft.AspNetCore.Identity.ISecurityStampValidator Lifetime: Scoped ImplementationType: Microsoft.AspNetCore.Identity.SecurityStampValidator 1[Microsoft.AspNetCore.Identity.IdentityUser]': Unable to resolve service for type 'X.Data.ApplicationDbContext' while attempting to activate 'Microsoft.AspNetCore.Identity.EntityFrameworkCore.UserOnlyStore 6[Microsoft.AspNetCore.Identity.IdentityUse r,X.Data.ApplicationDbContext,System.String,Microsoft.AspNetCore.Identity.IdentityUserClaim 1[System.String],Microsoft.AspNetCore.Identity.IdentityUserLogin 1[System.String],Microsoft.AspNetCore.Identity.IdentityUserToken 1[System.String]]'.) (Error while validating the service descriptor 'ServiceType: Microsoft.AspNetCore.Identity.ITwoFactorSecurityStampValidator Lifetime: Scoped ImplementationType: Microsoft.AspNetCore.Identity.TwoFactorSecurityStampValidator 1[Microsoft.AspNetCore.Identity.IdentityUser]': Unable to resolve service for type 'X.Data.ApplicationDbContext' while attempting to activate 'Microsoft.AspNetCore.Identity.EntityFrameworkCore.UserOnlyStore 6[Microsoft.AspNetCore.Identity.IdentityUser,X.Data.ApplicationDbContext,System.String,Microsoft.AspNetCore.Identity.IdentityUserClaim 1[System.String],Microsoft.AspNetCore.Identity.IdentityUserLogin 1[System.String],Microsoft.AspNetCore.Identity.IdentityUserToken 1[System.String]]'.) (Error while validating the service descr iptor 'ServiceType: Microsoft.AspNetCore.Identity.SignInManager 1[Microsoft.AspNetCore.Identity.IdentityUser] Lifetime: Scoped ImplementationType: Microsoft.AspNetCore.Identity.SignInManager 1[Microsoft.AspNetCore.Identity.IdentityUser]': Unable to resolve service for type 'X.Data.ApplicationDbContext' while attempting to activate 'Microsoft.AspNetCore.Identity.EntityFrameworkCore.UserOnlyStore 6[Microsoft.AspNetCore.Identity.IdentityUser,X.Data.ApplicationDbContext,System.String,Microsoft.AspNetCore.Identity.IdentityUserClaim 1[System.String],Microsoft.AspNetCore.Identity.IdentityUserLogin 1[System.String],Microsoft.AspNetCore.Identity.IdentityUserToken 1[System.String]]'.) (Error while validating the service descriptor 'ServiceType: Microsoft.AspNetCore.Identity.IUserStore 1[Microsoft.AspNetCore.Identity.IdentityUser] Lifetime: Scoped ImplementationType: Microsoft.AspNetCore.Identity.EntityFrameworkCore.UserOnlyStore 6[Microsoft.AspNetCore.Identity.IdentityUser,X.Data.ApplicationDbCo ntext,System.String,Microsoft.AspNetCore.Identity.IdentityUserClaim 1[System.String],Microsoft.AspNetCore.Identity.IdentityUserLogin 1[System.String],Microsoft.AspNetCore.Identity.IdentityUserToken 1[System.String]]': Unable to resolve service for type 'X.Data.ApplicationDbContext' while attempting to activate 'Microsoft.AspNetCore.Identity.EntityFrameworkCore.UserOnlyStore 6[Microsoft.AspNetCore.Identity.IdentityUser,X.Data.ApplicationDbContext,System.String,Microsoft.AspNetCore.Identity.IdentityUserClaim 1[System.String],Microsoft.AspNetCore.Identity.IdentityUserLogin 1[System.String],Microsoft.AspNetCore.Identity.IdentityUserToken`1[System.String]]'.)

This error ocurrs when you forget to enabling DbContext service:

// in this example, we use "Sqlite" to manage connection
services.AddDbContext<ApplicationDbContext>(options =>
                options.UseSqlite(Configuration.GetConnectionString("DefaultConnection")));

If you want to use SQL Server instead of Sqlite, you can add Microsoft.EntityFrameworkCore.SqlServer NPM package:

services.AddDbContext<ApplicationDbContext>(options =>
              options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

If you define ApplicationDbContext class in the class library project (Namespace: Your_main_project_namespace.Data) , when you refer it to the main project, you need to call MigrationsAssembly method with the namspace name of the main project:

services.AddDbContext<ApplicationDbContext>(options =>
              options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection"),
              actions => actions.MigrationsAssembly("Your_main_project_namespace")));

Note: The current version (5.0.0) of this package is applied to net5.0 , so if you're using netcoreapp3.1 , you can use version 3.1.10 instead. Don't try to upgrade to the lastest, it will crash your project. Such as: removing/replacing some obsolete method/class/interface... ( IWebHostEnvironment vs IHostingEnvironment ...) .

---

Case 6:

Value cannot be null. (Parameter 'connectionString')

This error may come from your connection string name in the file appsettings.json :

{
  "ConnectionStrings": {
    "MyConnection": "DataSource=app.db;Cache=Shared"
  }
}

In this example, we name the connection string with the name MyConnection , so when we try to get:

Configuration.GetConnectionString("DefaultConnection")

the exception will be thrown because there is no property name DefaultConnection .

---

Case 7:

This problem may come from the way to append a large of data files to project via copy-paste method using Finder (on Mac) or Explorer (on Windows). The general case is: Coping to wwwroot folder:

When Visual Studio is opening and some files are copied to wwwroot folder (or somewhere else in the project) successful, the project will be saved automatically. There is no way to stop it.

And the remaining time will be calculated based on:

• File count,
• file size,
• file type,
• the target folder (wwwroot, node_modules...) ,
• and your hardware (CPU, RAM, HDD or SSD).

So, be careful if you want to copy more than 5000 images or videos to wwwroot folder. If something goes wrong (I don't even know where the error comes from) , you cannot run the project. In this case, I suggest:

• Wait until your project completes saving/loading/restoring. DO NOT take any action to try to stop or prevent it.
• Right click the project and choose Edit Project File to edit .csproj file. In this file, if you catch some implementation like this:

<ItemGroup>
    <Content Include="wwwroot\">
      <CopyToPublishDirectory>Always</CopyToPublishDirectory>
    </Content>
</ItemGroup>

The tag <ItemGroup> which contains <Content> tag, and the <Content> tag mentions about wwwroot folder or some folder name that inherits from wwwroot folder. DELETE all of them (including the parent tag: <ItemGroup> ), save the file and wait until the file is saved/all packages are restored.

• Clean the project and buid/rebuild again.
• More action: If the building/loading speed of your project becomes very slow, try to right click on the target folder (in this case: wwwroot) and choose Exclude From Project . Then waiting until Visual Studio completes the action, and right click the folder to choose Include From Project again. Waiting action is required (the time to exclude/include may the same).