dotnet muli db context - database

Question

In my task (dotnet core, c#), it is necessary to select one of the databases and make some kind of manipulation in accordance with the query.
According with microsoft docs, it's look like:
public class db1 : DbContext, Idb
{
public db1(DbContextOptions options) : base(options)
{}
}
public class db2 : DbContext, Idb
{
public db2(DbContextOptions options) : base(options)
{}
}
In Startup.cs
services.AddDbContext<db1>(options =>
options.UseSqlServer(Configuration.GetConnectionString("db1")));
services.AddDbContext<db2>(options =>
options.UseSqlServer(Configuration.GetConnectionString("db2")));
This allows you to register in DI and access a specific database connection instance, but all databases are hardcoded. This is a poor code. How is it better to make registration in DI by id of a database and select from DI's service by this id in a controller?

Answer 1

It is not so bad because you can change the connection string according to your environment, having different versions of your appsetings.json (appsettings.dev.json, appsettings.release.json and so on and so forth)
On the other hand you coulduse these context in your controllers contructors, i.e
ctor 1:
public FirstController(db1 context)
ctor2:
public SecondController(db2 context)
maybe, alse, ctor3:
public ThirdController(db1 contextA, db2 contextB )
BUT:
a) consider naming conventions (Idb?? db1??)
b) Why would you like to have Two same-kind-of repositories ... Oh! Are you trying to have a Generic repository pattern?? Then your answer is here: https://github.com/Arch/UnitOfWork (Im using it and I'm very hapy with the result and the performance, I'll paste an example bellow)
Using IUnitOfWork:
In your controller:
public YourController(IUnitOfWork unitOfWork)
{
try
{
_unitOfWork = unitOfWork;
// seeding
var ItemRepository = _unitOfWork.GetRepository<Item>();
//ETC...
In your StartUp, in ConfigureServices, call this method:
private void AddEntityFrameworkAndDbContext(IServiceCollection services)
{
services.AddEntityFrameworkSqlServer();
var migrationsAssemblyName = typeof(YourContext).GetTypeInfo().Assembly.GetName().Name;
services.AddDbContext<YourContext>(options =>
{
options.UseSqlServer(Your.ConnectionString.NoMAtterHowYouGetIt,
sqlServerOptionsAction: sqlOptions =>
{
sqlOptions.MigrationsAssembly(migrationsAssemblyName);
sqlOptions.EnableRetryOnFailure(maxRetryCount: 5, maxRetryDelay: TimeSpan.FromSeconds(30), errorNumbersToAdd: null);
}); // Man, this is for free, I spent days getting it to work
},
ServiceLifetime.Scoped // Showing explicitly that the DbContext is shared across the HTTP request scope (graph of objects started in the HTTP request)
).AddUnitOfWork<YourContext>();
}
And in Configure try something like:
app.EnsurePopulated(app.ApplicationServices.GetRequiredService());
I hope it helps you,
Juan