无法创建 'ApplicationDbContex' Blazor ASP.NET Core 6.0 类型的对象

Question

我在 Blazor ASP.NET Core web 中创建一个 Web 应用程序 ASP.NET Core 6，当我迁移数据库时，我遇到了这个错误：

Unable to create an object of type 'ApplicationDbContext'. For the different patterns supported at design time, see https://go.microsoft.com/fwlink/?linkid=851728

我需要一个解决方案 - 这是我的代码：

Program.cs

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddRazorPages();

builder.Services.AddDbContext<ApplicationDbContext>(options =>
            options.UseSqlServer(builder.Configuration.GetConnectionString("Prueba")));

builder.Services.AddDefaultIdentity<ApplicationUser>()
                   .AddRoles<IdentityRole>()
                   .AddEntityFrameworkStores<ApplicationDbContext>();

builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
                   .AddJwtBearer(options =>
                   {
                       options.TokenValidationParameters = new TokenValidationParameters
                       {
                           ValidateIssuer = true,
                           ValidateAudience = true,
                           ValidateLifetime = true,
                           ValidateIssuerSigningKey = true,
                           ValidIssuer = builder.Configuration["JwtIssuer"],
                           ValidAudience = builder.Configuration["JwtAudience"],
                           IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(builder.Configuration["JwtSecurityKey"]))
                       };
                   });

builder.Services.AddAuthorization(config =>
 {
    config.AddPolicy(Policies.IsAdmin, Policies.IsAdminPolicy());
    config.AddPolicy(Policies.IsUser, Policies.IsUserPolicy());
 });
builder.Services.AddSignalR();

builder.Services.AddMvc().AddNewtonsoftJson(options =>
           options.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore);
builder.Services.AddControllersWithViews();
//builder.Services.AddRazorPages();
builder.Services.AddResponseCompression(option =>
{
    option.MimeTypes = ResponseCompressionDefaults.MimeTypes.Concat

    (new[] { "application/octet-stream"
    });
});

var app = builder.Build();

using (var scope = app.Services.CreateScope())
{
    var services = scope.ServiceProvider;

    SeedData.Initialize(services);
}

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.UseDeveloperExceptionPage();
    app.UseWebAssemblyDebugging();
}
else
{
    app.UseExceptionHandler("/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.UseBlazorFrameworkFiles();
app.UseStaticFiles();

app.UseRouting();

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


app.MapRazorPages();
app.MapControllers();
app.MapFallbackToFile("index.html");
app.UseEndpoints(endpoints =>
{
    endpoints.MapHub<UsuariosHub>("/UsuariosHub");
});
app.Run();

ApplicationDbContext.cs

using Microsoft.AspNetCore.Identity.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore;
using ProyectoBP.Shared.Models;

namespace ProyectoBP.Server.Data;

public class ApplicationDbContext : IdentityDbContext<ApplicationUser>
{
    public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
      : base(options)
    {
    }

    protected override void OnModelCreating(ModelBuilder builder)
    {
        base.OnModelCreating(builder);
    }

    public DbSet<Movie> Movies { get; set; }
}

SeedData.cs

using Microsoft.EntityFrameworkCore;
using ProyectoBP.Server.Data;

namespace ProyectoBP.Shared.Models
{
    public static class SeedData
    {
        public static void Initialize(IServiceProvider serviceProvider)
        {
            using (var context = new ApplicationDbContext(
                serviceProvider.GetRequiredService<
                    DbContextOptions<ApplicationDbContext>>()))
            {
                context.SaveChanges();

                if (context == null || context.Movies == null)
                {
                    throw new ArgumentNullException("Null ApplicationDbContext");
                }

                // Look for any movies.
                if (context.Movies.Any())
                {
                    return;   // DB has been seeded
                }
                  
                context.SaveChanges();
            }
        }
    }
}

appsettings.json

{
  "AllowedHosts": "*",
  "ConnectionStrings": {
    "DefaultConnection": "Data Source=ISMAEL-PC;Initial Catalog=BP;Integrated Security=False;uid=JoseD;password=Laugama2021.",
    "Prueba": "Data Source=ISMAEL-PC;Initial Catalog=BP;Integrated Security=true"
  },
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "Microsoft.Hosting.Lifetime": "Information"
    }
  }
}

我没有 StartUp Class 因为显然 ASP.NET Core 6 不需要它

Answer 1

你应该更换

serviceProvider.GetRequiredService<DbContextOptions<ApplicationDbContext>>()

到

serviceProvider.GetRequiredService<ApplicationDbContext>()

在 SeedData class :

using Microsoft.EntityFrameworkCore;
using ProyectoBP.Server.Data;
namespace ProyectoBP.Shared.Models
{
    public static class SeedData
    {
        public static void Initialize(IServiceProvider serviceProvider)
        {
            using (var context = serviceProvider.GetRequiredService<ApplicationDbContext>())
            {
                context.SaveChanges();

                if (context == null || context.Movies == null)
                {
                    throw new ArgumentNullException("Null ApplicationDbContext");
                }

                // Look for any movies.
                if (context.Movies.Any())
                {
                    return;   // DB has been seeded
                }
                  
                context.SaveChanges();
            }
        }
    }
}

Answer 2

在 DbContext 上添加无参数构造函数 (ApplicationDbContext.cs)

publicApplicationDbContext() { }
确保将默认启动项目设置为 WebApplication

或在更新命令末尾添加 -s {Satrtup 项目名称}

将 Microsoft.EntityFrameworkCore.Design 包添加到 WebApplication 项目

Answer 3

我通过检查 include prerelease 选项解决了我的问题，因为我在预发布版本中使用 ASP.NET Core 6，但我试图迁移到当前的稳定版本。所以我希望这可以帮助你。

Answer 4

临时 re-register 从 AddSingleton 和 AddScoped 到 AddTransient 的所有服务。它对我有用。

无法创建 'ApplicationDbContex' Blazor ASP.NET Core 6.0 类型的对象

Unable to create an object of type 'ApplicationDbContex' Blazor ASP.NET Core 6.0

entity-framework

asp.net-core

blazor

asp.net-blazor

blazor-webassembly