没有为此DbContext配置数据库提供程序

Question

我最近将我的项目更新为最新版本的Entity Framework Core（+ VS2017）。当我尝试更新数据库时，我收到以下错误消息。错误消息很明显，但似乎是错误的。我的ConfigureServices中有一个AddDbContext（参见下面的代码）。

我错过了什么？

错误

> dotnet ef database update --verbose

Finding DbContext classes...
Using context 'ApplicationDbContext'.

System.InvalidOperationException: No database provider has been configured for this DbContext. A provider can be configured by overriding the DbContext.OnConfiguring method or by using AddDbContext on the application service provider. If AddDbContext is used, then also ensure that your DbContext type accepts a DbContextOptions<TContext> object in its constructor and passes it to the base constructor for DbContext.

启动

public void ConfigureServices(IServiceCollection services) {
  services.AddDbContext<ApplicationDbContext>(options =>
    options.UseSqlServer(this.Configuration.GetConnectionString("DefaultConnection")));

的csproj

<PackageReference Include="Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore">
  <Version>1.1.0</Version>
</PackageReference>
<PackageReference Include="Microsoft.AspNetCore.Identity.EntityFrameworkCore">
  <Version>1.1.0</Version>
</PackageReference>
<PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer">
  <Version>1.1.0</Version>
</PackageReference>
<PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer.Design">
  <Version>1.1.0</Version>
  <PrivateAssets>All</PrivateAssets>
</PackageReference>
<PackageReference Include="Microsoft.EntityFrameworkCore.Tools">
  <Version>1.0.0-msbuild1-final</Version>
  <PrivateAssets>All</PrivateAssets>
</PackageReference>
<PackageReference Include="Microsoft.EntityFrameworkCore.Design">
  <Version>1.1.0</Version>
</PackageReference>

Answer 1

你必须删除默认构造函数。换句话说，参数less constructor.After all all将按预期工作。

注意：原因是，在运行时调用参数less构造函数而不是public MyDbContext(DbContextOptions options) : base(options) {}。