c# - 升级到 ASP.NET Core 2.0 后无法创建迁移

Question

升级到 ASP.NET Core 2.0 后，我似乎无法再创建迁移。

我得到了

"An error occurred while calling method 'BuildWebHost' on class 'Program'. Continuing without the application service provider. Error: One or more errors occurred. (Cannot open database "..." requested by the login. The login failed. Login failed for user '...'"

和

"Unable to create an object of type 'MyContext'. Add an implementation of 'IDesignTimeDbContextFactory' to the project, or see https://go.microsoft.com/fwlink/?linkid=851728 for additional patterns supported at design time."

我之前运行的命令是 $ dotnet ef migrations add InitialCreate --startup-project "..\Web"(来自具有 DBContext 的项目/文件夹)。

连接字符串:"Server=(localdb)\\mssqllocaldb;Database=database;Trusted_Connection=True;MultipleActiveResultSets=true"

这是我的 Program.cs

 public class Program
{
    public static void Main(string[] args)
    {
        BuildWebHost(args).Run();
    }

    public static IWebHost BuildWebHost(string[] args) =>
       WebHost.CreateDefaultBuilder(args)
           .UseStartup<Startup>()
           .Build();
}

Answer 1

您可以在您的 Web 项目中添加一个实现 IDesignTimeDbContextFactory 的类。

示例代码如下:

public class DesignTimeDbContextFactory : IDesignTimeDbContextFactory<CodingBlastDbContext>
{
    public CodingBlastDbContext CreateDbContext(string[] args)
    {
        IConfigurationRoot configuration = new ConfigurationBuilder()
            .SetBasePath(Directory.GetCurrentDirectory())
            .AddJsonFile("appsettings.json")
            .Build();
        var builder = new DbContextOptionsBuilder<CodingBlastDbContext>();
        var connectionString = configuration.GetConnectionString("DefaultConnection");
        builder.UseSqlServer(connectionString);
        return new CodingBlastDbContext(builder.Options);
    }
}

然后，导航到您的数据库项目并从命令行运行以下命令:

dotnet ef migrations add InitialMigration -s ../Web/

dotnet ef database update -s ../Web/

-s stands for startup project and ../Web/ is the location of my web/startup project.

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