實體框架核心無法添加遷移

Question

執行dotnet ef add migration InitialMigration命令會給出此錯誤A suitable constructor for type 'Vega.Repository.VegaContext' could not be located. Ensure the type is concrete and services are registered for all parameters of a public constructor. A suitable constructor for type 'Vega.Repository.VegaContext' could not be located. Ensure the type is concrete and services are registered for all parameters of a public constructor.

我在Startup類上的ConfigureServices方法如下：

public void ConfigureServices(IServiceCollection services)
{            
   services.AddMvc();       
   services.AddScoped<IUnitOfWork, UnitOfWork>();
   var connectionString = Configuration.GetConnectionString("VegaConnection");
   services.AddDbContext<VegaContext>(options =>
            options.UseSqlServer(connectionString));
}

VegaContext類是：

public class VegaContext : DbContext
{
    VegaContext(DbContextOptions<VegaContext> options):base(options)
    {}
    public DbSet<Make> Makes { get; set; }
}

csproj文件的一部分是：

<ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.All" Version="2.0.5" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="2.0.1" />
    <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="2.0.2" />
</ItemGroup>

<ItemGroup>
    <DotNetCliToolReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Tools" Version="2.0.2" />
    <DotNetCliToolReference Include="Microsoft.EntityFrameworkCore.Tools.DotNet" Version="2.0.1" />
</ItemGroup>

Answer 1

如果您的代碼正是您發布的代碼，則解決方案非常簡單。 只需將您的DbContext-constructor公開，一切就可以了：

public class VegaContext : DbContext
{
    public VegaContext(DbContextOptions<VegaContext> options):base(options) { }
    public DbSet<Make> Makes { get; set; }
}