没有为此DbContext配置数据库提供程序 [英] No database provider has been configured for this DbContext

问题描述

我最近将项目更新为最新版本的Entity Framework Core（+ VS2017）。当我尝试更新数据库时，出现以下错误消息。该错误消息是明确的，但它似乎是错误的。我的ConfigureServices中确实有一个AddDbContext（请参见下面的代码）。

I recently updated my project to the latest version of Entity Framework Core (+VS2017). When I try to update the DB I get the following error message. The error message is clear, but it appears to be wrong. I do have a AddDbContext in my ConfigureServices (see code below).

我缺少什么？

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")));

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>

推荐答案

您必须删除默认构造函数。换句话说，参数较少的构造函数。之后所有这些都将按预期工作。

You have to remove the default constructor.In other words parameter less constructor.After that all will work as expected.

注意：在运行时调用参数较少的构造方法，而不是此 public MyDbContext（DbContextOptions options）：base（options）{} 。

Note : The reason for that is, the parameter less constructor is being called at run time instead of this public MyDbContext(DbContextOptions options) : base(options) {}.

这篇关于没有为此DbContext配置数据库提供程序的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！