Expose IDbConnection through DI

[mdockal]

Fixes #2757, and fixes #2248. Ran into some issues with async /await inside lambda expression, had to hack it a little bit.

[sebastienros]

That will be an issue. You will need to create a wrapper around the connection (implementing) idbconnection that will be built using the session. This way we can return it without asynchronous calls. Also, register this instance with the interface in the AddScoped call so it's a lazy initialization instead.

[mdockal]

@sebastienros I am not sure what you mean? Why are we using async anyway just for a connection object? I (speaking as the end - developer trying to extend the data model) don't want an open connection nor a transaction. My Micro ORM / ORM will handle that or I will handle it explicitly in the module. I don't think is a good idea to open a connection without explicitly trying to read or update the data.

So I looked at the DemandAsync() code and it turns out it is calling DBConnection.OpenAsync() that is the reason why it is async. However, I did find something in DemandAsync() that was exactly what I think I and other developers need.

_connection = _store.Configuration.ConnectionFactory.CreateConnection() as DbConnection;

So if I use the IStore instance to simply get the connection factory we get something like this:

 services.AddScoped(sp =>
                {
                    var store = sp.GetService<IStore>();

                    if (store == null)
                    {
                        return null;
                    }

                    var connection = store.Configuration.ConnectionFactory.CreateConnection();

                    return connection;
                });

I think it's all that really needed, and no async / await method Calls!

[sebastienros]

You have a GetAwaiter().GetResult() line which will be called from an async path (a controller for instance).

[mdockal]

You have a GetAwaiter().GetResult() line which will be called from an async path (a controller for instance).

Agreed, I had read that wasn't a really good way to do things.

If we simply use:
var connection = store.Configuration.ConnectionFactory.CreateConnection();

We don't need to do async because all we need is the IDbConnection instance.

[sebastienros]

It's not the issue. The issue is that someone will do Resolve<IDbConnection>(), and the code it will run will contain a blocking call to DemandAsync().

It might be necessary to use a provider interface with a GetConnectionAsync().

[jtkech]

@mdockal i re-added the .gitignore but without the added line directly in your repo, so that here we now have only one modified file.

[mdockal]

@mdockal i re-added the .gitignore but without the added line directly in your repo, so that here we now have only one modified file.

Thanks @jtkech I am learning how to do git. I come from using Visual Source Safe and VSTFS background so git doesn't work like I expect it to.

[mdockal]

I created an IDbConnectionAccessorr interface and DbConnectoinAccessor and registered it. The developer will call IDbConnectionAccessor.GetConnectionAsync() which calls Session.DemandAsync() and returns an open IDbConnection async for the developer.

public class SomeController : Controller
{
    private IDbConnectionAccessor _connectionAccessor;

    public SomeController(IDbConnectionAccessor connectionAccessor)
    {
          _connectionAccessor = connectionAccessor
    }
    
    public async Task<IActionResult> Index()
    {
        IDbConnection connection = await _connectionAccessor.GetConnectionAsyc();
    }
}

[sebastienros]

Last details and it's all good.