Design Time DbContext Factory - Class Library how to get connection string from UserSecrets in a cla-CodePudding

I have separated my Database project as a class library. And I am defining a IDesignTimeDbContextFactory implementation. I want to use user-secrets to keep the config settings. I get an error as follows. How can i make this setup work?

Note: I have already setup the user-secrets for the class library project. And my user secrets has the necessary values:

{
  "ConnectionStrings:CatalogDbContext": "Server=(localdb)\\\\mssqllocaldb;Database=Catalog;Trusted_Connection=True;MultipleActiveResultSets=true"
}

Project Structure:

Catalog
|---API(Web API)
|---Data(Class Lib)
    |- appsettings.json
    |- IDesignTimeDbContextFactory<CatalogDbContext>

Appsettings.json

{
  "ConnectionStrings": {
    "CatalogDbContext": ""
  }
}

public class CatalogDbContextFactory : IDesignTimeDbContextFactory<CatalogDbContext>
{
    public CatalogDbContext CreateDbContext(string[] args)
    {
        IConfigurationRoot configuration = new ConfigurationBuilder()
            .SetBasePath(Directory.GetCurrentDirectory())
            .AddJsonFile("appsettings.json")
            .Build();

        var dbContextOptionsBuilder = new DbContextOptionsBuilder<CatalogDbContext>();
        var connectionString = configuration.GetConnectionString(nameof(CatalogDbContext));
        dbContextOptionsBuilder
            .UseSqlServer(connectionString);

        return new CatalogDbContext(dbContextOptionsBuilder.Options);
    }
}

This command fails with an error:

Catalog.Api> dotnet ef migrations add Catalog.Initial --project ..\Catalog.Data\Catalog.Data.csproj --verbose

Finding DbContext classes in the project...
Found DbContext 'CatalogDbContext'.
Using DbContext factory 'CatalogDbContextFactory'.
System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
 ---> System.ArgumentNullException: Value cannot be null. (Parameter 'connectionString')
   at Microsoft.EntityFrameworkCore.Utilities.Check.NotEmpty(String value, String parameterName)
   at Microsoft.EntityFrameworkCore.SqlServerDbContextOptionsExtensions.UseSqlServer(DbContextOptionsBuilder optionsBuilder, String connectionString, Action`1 sqlServerOptionsAction)

I can clearly say this is because the connectionstring is empty. The user secrets configuration provided is not added to the list of providers. I don't know what the setup will look like to add user secrets to a class library project. Please help!

CodePudding user response：

I tried as you mentioned and repeated your error in my case

then I modified the appsettings.json in webapi project and added the migration successfully this time,it still read the jsonfile in your webapi project