Injecting Env Conn String into .NET Core 2.0 w/EF Core DbContext in different class lib than Startup prj & implementing IDesignTimeDbContextFactory

Question

I honestly cannot believe how hard this is...first off the requirements that I am going for:

• Implementing Entity Framework Core 2.0\' IDesignTimeDbContex

Answer 1

I am a bit confused with your question. Are you using dependency injection for the DbContext or are you trying to initialize and construct the context ad hoc?

I am doing what you have described in one of my solutions. Here is my solution structure:

• Corp.ApplicationName.Data
• Corp.ApplicationName.Web

Startup.cs

public Startup(IHostingEnvironment env)
{
    IConfigurationBuilder builder = new ConfigurationBuilder()
        .SetBasePath(env.ContentRootPath)
        .AddJsonFile("appsettings.json", false, true)
        .AddJsonFile($"appsettings.{env.EnvironmentName}.json")
        .AddEnvironmentVariables();
    // ...
}

public void ConfigureServices(IServiceCollection services)
{
    // Add framework services.
    services.AddDbContext(
        options => options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection"),
        sqlOptions => sqlOptions.EnableRetryOnFailure()));

    // SQL configuration for non-injected dbcontext
    DbContextOptionsBuilder builder = new DbContextOptionsBuilder();
    builder.UseSqlServer(Configuration.GetConnectionString("DefaultConnection"));
    services.AddSingleton(builder.Options);

    // ...
}

MyDbContext.cs

public class MyDbContext : IdentityDbContext
{
    public MyDbContext(DbContextOptions options) : base(options) { }
}

If you are not using dependency injection to pass the DbContext, you can access the SQL properties by injecting DbContextOptions instead.

In this example, the appsettings file is only every read once and everything just works.